In the third episode of Statistically Speaking we talk to Professor Sir Ian Diamond, the UK’s National Statistician, and Dr Louisa Nolan, Chief Data Scientist at the ONS Data Science Campus about the past, present and future of stats. We explore how the pandemic has been transformative for the use and understanding of public data and how the data revolution and the fight against COVID are changing UK stats forever. Transcript: MILES FLETCHER  Welcome to Statistically Speaking: the podcast where numbers talk and we talk to the people behind them. In this third episode, we meet professor Sir Ian Diamond, UK National Statistician and Dr Louisa Nolan, Chief Data Scientist at the ONS Data Science Campus. We explore how the pandemic has been transformative for the use and understanding of public data and how the data revolution and the fight against COVID are together changing UK stats forever. But to begin I asked Sir Ian what led him to a life of stats    SIR IAN DIAMOND  Okay, well, I'm going to be absolutely honest Miles: genetics. I have no idea why I was always interested in numbers and statistics but I always was. And so something in my genes said I like numbers. Something else in my genes said I like numbers but numbers which have an application and a practical application. And that led me to not only be interested in statistics, but to study statistics and then to work as a statistician in academia for some decades, but always interested in numbers and their application to policy and to improving the lives of people. And if you take that as a starting point, then it's what I've always done, and led me to at times work in partnership with different government departments. And that led me to partnerships with ONS, which has led me here.    MILES FLETCHER  A lot of people sort of regard statistics as numbers on a page, something that can seem quite abstract, but they exist of course to help people make important decisions. Can you think of an example in your pre-ONS career, your pre-National Statistician life, where you first used numbers and statistics to actually help solve a real-world problem?    SIR IAN DIAMOND  Well, yes, I mean, if I go back to the very early 1980s, at that time, the observation was made, that there had been a decline in the number of children born in the UK. That was going to be a decline of around 30% in the number of 18-year-olds, and it was suggested that therefore there would be a reduction in the demand for higher education. Working initially with Fred Smith and then subsequently on my own, I was able to project the future demand for higher education, on the basis of some assumptions that the number of women going into higher education would increase, that there would be social mobility in the country as a whole. And also, that there would be an increase in what we now call widening participation. When you bring all those things together, you get a very, very different number for the demand for higher education than from simply following the number of births. And that had an impact alongside work that other people did on influencing policy for higher education.    MILES FLETCHER  So a busy, very successful academic career is followed then by stint as National Statistician. You're in the job, what six months last March, just as the pandemic, as we as we came to know, was starting to break. At what point did you realise that it was going to be as big as it turned out to be and that a very special response was going to be required from the statistical system, the UK statistical system, ONS, and all the statisticians in government departments, the system that you're responsible for?    SIR IAN DIAMOND  I mean, I think early in 2020 Miles. We identified, very sadly, the first death from COVID at the beginning of March 2020. We now think there might have been one earlier but, you know, I think very early on we at ONS recognised that this was something that the statistical community needed to really step up for, not least working with the wider international community to define a cause of death as being due to COVID. I'd say March 2020 is when we really became aware there was going to need to be some really fast and accurate estimates of all kinds of things around the pandemic, whether it was impacting on the economy, or indeed the pandemic itself, and that led to us in April to putting together a survey which estimated both prevalence but also the level of antibodies, and subsequently now of course, issues around vaccination.    MILES FLETCHER  So it was a very important decision point where it was realised that the traditional, if you put it that way, the main data sources that ONS and others in government were producing were not going to be enough to measure a very, very important factor in this, that's actually how many people have got the virus at any at any one time. What point did that arise and what happened next?    SIR IAN DIAMOND  We had a conversation early in April. We said ONS could use our ability to be able to design nationally representative surveys and to pivot some of those designs into collecting the biomedical data that are important in order to be able to identify both prevalence and antibodies, but we will only do so in partnership with other experts. And so we very, very quickly set up partnerships with the University of Oxford, the Wellcome Trust, and the Department of Health and the Office of Life Sciences. We were able to set up a team that in one week, was able to move from a decision to go for it, to design, to ethics to the first field workers collecting some data.    MILES FLETCHER  And it was mounting, what was by anybody's standards, a huge field operation, as you say, in very short order to get around households up and down the United Kingdom eventually, when the survey was running at full scale. To do that very, very quickly, a huge operation…    SIR IAN DIAMOND  Two stages Miles: the first of which is we stood it up as a nationally representative sample, which would make estimates for England. And, you know, it takes a lot of things at pace. So getting from the field workers getting the swabs to the laboratories, getting the tests, getting them back, doing some really quite sophisticated statistical analysis to make estimates. Getting all that done requires a lot of logistics, and I think the team deserves an enormous pat on the back for so doing. And then that success led to the scaling up. So that we can make original estimates so that we can make age-specific estimates. And we were able to do that. But then that was a huge scale up in September of 2020 and I think again, the logistics of scaling that up was incredibly challenging, but successful. And at the same time working with our colleagues in Scotland, Wales and Northern Ireland, to be able to produce estimates for those administrations too was something that I'm very proud of.    MILES FLETCHER  And the record shows exactly what was achieved during those pressured early months of the pandemic. And of course, right at the start there were plenty of people around who doubted whether the statistical system, whether the ONS and others were really capable of doing that job. Was it satisfying to confound those critics?    SIR IAN DIAMOND  I didn't hear them, I just got on and did it, to be absolutely honest, Miles. I knew what we could achieve in terms of both the survey which was able to measure prevalence and antibodies, but also the social survey because you need to know how people are feeling about the restrictions. You need to know how people are feeling about the pandemic. Were they anxious or not? And then as people started to talk about, for example, face coverings. What were people's attitudes to those things and, and were people adhering to the restrictions? So, there was a social survey, that was producing weekly estimates as well. That was incredibly important, and we were producing economic statistics, as well. So I have to say it wasn't a question of was the statistical system standing up and delivering a survey to estimate prevalence of the pandemic.  But it was addressing a whole set of other questions, which required not only statistical collection, but in some cases, further analysis, and data linkage and a whole range of sophisticated statistical methods to be able to provide information for the government and for the population so that they understood exactly where we were at any time.    MILES FLETCHER  And what do you think that all that has done for the general trust the public have in the statistics that they see from us or from the media?    SIR IAN DIAMOND  ONS has always been a very trusted organisation. I mean, one of the important things that we have in the UK is the independence of the ONS and I think that’s incredibly important and the public in all the surveys that we have done over many years have demonstrated great trust in the statistics that we produce. And I think that the public has continued to show that trust over the pandemic. And I hope although at this stage I stress I'm hoping, that the public will feel that the ONS has delivered during the pandemic and therefore will be prepared to continue to trust the ONS in the future.    MILES FLETCHER  Talking about the public and involvement, coinciding with this pandemic has been census of course in England and Wales and we asked every household once again to complete the census. Again, at the beginning, some said it couldn't be done because of the pandemic and others even more said it shouldn't be done because of the cost. How has it all gone? And will it tell us what we now urgently need to know about our population?   SIR IAN DIAMOND   We had a really very good and very strong response. We're now in the process of doing the analysis so that we can produce really accurate results and that's going to be incredibly important. Should we do a census? Well, I think a census is a statement of great confidence from a country that is prepared to say that on one day, this is a picture of what that country is and how many people there are and their characteristics. And that is so important for all kinds of reasons. So yes, it was incredibly important I think that we did. Yes, it was incredibly important that we did it at the time of the pandemic, because we needed to know where we were at that time. Of course, we will be working very hard to update our statistics over time to really understand the post pandemic world. I'd have to say also that you know, the cost is high, no question. And we will be working very, very hard over the next 18 months or so, to produce a set of recommendations as to the future of population data collection. Do we need another census or can we do things that administrative way. In 2014 we thought about this with regards to 2021 and a really good report done by the late Chris Skinner, together with John Hollis and Mike Murphy, recommended that this census that we've just done, digital first census, should go ahead, but we should aim to make a recommendation about the future. And that's what we're planning to do. It will require support from many other parts of government. I'm confident that we will get that support. And the one thing I can say Miles is that over the next 18 months or so we'll be working flat out to be able to make a recommendation that is extremely tight and extremely evidence based.    MILES FLETCHER  Now this whole question of whether there should be another census, actually it chimes with a reaction that we saw coming back from the public, and we did certainly get a good response rate. We reckon 97 percent of households did take part in the census and that's as good a response as there's ever been - perhaps there was a certain advantage to holding it during lockdown even - but some people asked why they have to fill in this census because surely the government should already have all this information to hand by now. How far are we down the road to be able to gather all the information from other sources already as many countries do.     SIR IAN DIAMOND   Well other countries do and other countries for example, particularly those in Scandinavia require a Population Register where you have to if you leave the country, come back into the country, you have to register that you are there. And if you move you have to register. We don't do that. So we do not require you to register that, for example, you have moved house or register with the Office for National Statistics. You may register with the land registry but if you don't, if you just move, we don't require you to register that. Interestingly, there is no one source for occupation in this country other than the census. So, while you may think that data are held everywhere, Miles, they actually aren't. And so, while there are a lot of government data, there are no single sources which cover a lot of the things that a Census does and also there are one or two questions that one has in the census which are attitudinal, for example. So, you ask about well being. Well the only way you can ask people about wellbeing is to ask them, so you actually need to collect those data on a census. So there's a whole set of things that we ask on the census that very simply we don't ask elsewhere. And therefore, it's important, I think that we do get those data.    MILES FLETCHER  And of course data has to be fast to be effective now, or certainly faster. During the pandemic again we've seen advances in how new data sources have been used: anonymised credit card data, traffic camera data, mobile phone data, shipping data to provide these really fast readings of economic impact. Novel and brought in, in some cases, and as a specific response to the urgencies of the pandemic. But will these last now?     SIR IAN DIAMOND  One hundred percent. I think one of the things we've seen over the last few years has been the increase in born digital data, and we need to recognise the potential benefits of those data for our understanding of society and the economy, and indeed the environment and we need to be using them at pace in every way possible. And asking the question, do they replace things that we always have? Or are they in addition? And if they are, in addition, are they really adding value? Very easy to get involved in what you might call a data deluge. Yeah, there's loads of data out there so we’d better have it. I think you have to be very, very focused on whether any particular data add value and insight to the subject under study. If they do, then I think that it's important for us to use them and to access them. If they're just simply adding some more data then we do not need to follow them up. So data for insight, not data for data's sake.    MILES FLETCHER  So we've had two years driven mainly, but not wholly by the pandemic, but two years of incredible progress in our statistical system. Looking to the next decade, what comes next, what do you think we're going to see in statistics and data, how it's going to be used and what sort of issues are we going to be addressing?    SIR IAN DIAMOND   We will be able to process ever bigger datasets and to do so ever faster. So all the kinds of things we have been talking about, about more digital data, analysis of texts, as well as numbers and data produced at speed and at pace will be the norm. But that doesn't stop us wanting to continue to collect some pretty important data, for example, GDP or inflation data and to do so, perhaps, in a new way. In the last year we've calculated GDP using some innovative data sources, but in a way which enables those long time series that we started talking about at the beginning of this conversation Miles, to be maintained. I think it’s incredibly important that we do maintain time series while at the same time produce evermore exciting and new data sources. And I return finally to the point that we will still want attitudes. If you want attitudes, we'll need to continue to do surveys. So I think it’s an exciting time, one of the other areas that I think we will see, real progress is improved data visualisation and improved interoperability with people. And I think that's important when it comes back to trust, if people are able to go on and manipulate the data themselves very, very easily, then again, the transparency and the openness and the use of data will be something that will remain at the heart of what we do.    MILES FLETCHER  That's Sir Ian Diamond, the National statistician. Now if there was one single development that made the ONS and perhaps the whole of the UK statistical system ready to cope with the pandemic, it was arguably the ONS Data Science Campus. Established in 2017 its mission is to work at the frontier of Data Science and Artificial Intelligence, building skills and applying tools, methods and practices it says, to create new understanding and improve decision making for the public good. So what does that all mean in practice, and what has the campus achieved in its first four years? Questions I put to Dr. Louisa Nolan, its chief data scientist. Louisa to take it from the top as it were: tell us, what is the data science campus and what are you out to achieve?     LOUISA NOLAN  The data science campus was set up four and a half years ago, and our mission is to explore new types of data, new types of technology, new techniques in data science, to make sure that we're making the most out of the data that's available, the ever increasing types of data that are available to us. And we also build capability in data science not just in ONS but across government and the wider public sector as well. So data science is really about the analysis of that data, getting that data together. But we need to get hold of the data. We need the right tools and platforms to use that data, particularly big data. It's about testing those technologies and how we do that to build those insights as well.     MILES FLETCHER  And when does data that you harvest, when does it become statistics?    LOUISA NOLAN  That's a really interesting question. And different people probably would give different answers. Statistics, I would say is a summary. So it's a summary, it might be the average the mean, or it might be a trend, it's looking at the overall picture, whereas data might be your input. So the satellite picture or the information somebody's given on the census, and statistics really is turning it into something that we can then understand broadly, what's going on and why those things are going on.     MILES FLETCHER  And it's your job then, in essence, to find how best to use that, those mountainous volumes of data and transfer them into usable, useful statistics and insights.     LOUISA NOLAN   Absolutely, and there's the technical part of that the techniques but also understanding those new types of data, understanding their quality and their bias and how we can best use them so that we produce something that's useful for decision making and not misleading.     MILES FLETCHER  The data science campus has been around for just a couple of years really, but what have you achieved in the time since it's been running?     LOUISA NOLAN   We've achieved a lot. So on the capability side we've set up data analytics apprenticeships, the graduate data science programme, the data masterclass, which is about teaching senior leaders data literacy, we've delivered face to face training, we've trained more than 600 analysts across government to be data scientists in that time. We've built data science community activities, and then we've also delivered a vast range of projects, including things around faster indicators, counting cows from space, text analysis to help automate and understand big government consultations. So it's been a really wide range of stuff.     MILES FLETCHER  What have you been doing, for example, with economic statistics?     LOUISA NOLAN  So we've been doing some really interesting stuff with economic statistics. Back two years ago, seems like it was longer ago but I think it was only two years ago, we were asked to see if we could find faster indicators which would help to kind of test the health of the economy much earlier than our GDP and official outputs. And this isn't as a replacement for GDP, just to get some faster information a bit earlier. So we had a look at what was available. And we wanted to make sure that we had data that was high frequency and low latency, obviously, if we want to understand what's going on bit quicker. But also to make sure that it had some kind of relationship to economic concepts. In the past people have looked at things like lipstick sales, or men's pants sales or…    MILES FLETCHER  Counted cranes?     LOUISA NOLAN   Counting cranes! Counting cranes is maybe slightly better, but not all of these are very robust, and actually they're terribly subjective. And if you look at them over the long term, they don't really work. So we wanted things that really related to economic concept, even if they weren't the same as GDP. We're not trying to measure GDP. So we had a look at the various datasets that were available and the first set of faster indicators that we produced covered three different datasets, all of them really interesting in their own right. So the first one was creating a diffusion index from VAT returns. So a diffusion index just tells you the proportion of businesses whose turnover have gone up since they last reported, and obviously if that starts to drop off, that's a bit of a warning signal and you might want to go and have a bit more of a look and see what's going on or why that's happening. The other two were really different. We've used VAT data before, but the other two were really different for ONS. Firstly, road traffic data. So this comes from sensors in roads, particularly used for active traffic management, and it counts the number of vehicles passing those sensors and you can also tell how big the vehicles are, so you can separate out cars from HGVs. And we think this ought to be quite a good indicator of what's going on in the economy. Because the amount of stuff moving around the country, people travelling to and from work, quite interesting and you'd expect that to be related to economic health and the movement of people and goods. And then the last one was perhaps the most interesting dataset because it's the biggest. It’s a global dataset on shipping. Every ship has a tracker. When it's in motion, if it's above a certain size, when it's in motion, it has to say where it is every second and then when it's at rest it needs to say where it is every couple of minutes. So this is an amazing dataset that tracks all the big ships. So we had a look at ships coming into UK ports, the number of visits, the type of ships coming in and how long they stayed there for. We created, I think it was about 300 different time series from these and published them very quickly. The first time that ONS had done something like this, possibly the first time in the world that this kind of faster indicators had been published by a national statistics institute on a regular basis. Really interesting data. And I think that kind of set the scene. So we've gone from those initial three datasets. Over COVID, huge appetite for faster information because things were happening so rapidly, lots of changes in the economy that were unpredicted two years ago. And so both data science campus and ONS have built on that initial faster indicator output. There's now a suite of I think more than ten different faster indicators based on things like job vacancies, footfall, traffic, camera information, all kinds of things that are feeding into that picture of what's going on very rapidly. High frequency, not much delay between the data and the reporting.     MILES FLETCHER  To what extent has the pandemic then hastened the pace of progress in the data science campus, and to what extent have the indicators that you produced been corroborated or vindicated by the subsequent classical data that ONS produce?    LOUISA NOLAN  And so as COVID hit, obviously, there was a huge desire to know what was going on how well people were complying with restrictions. Were people really moving about or have they complied and stopped moving about, and also understanding the impact of that on the economy. So the campus was well placed because of our skills and the way we're set up to rapidly pick up some new datasets and have a look at them. So we very quickly got some mobility dataset. So this is about how the bulk of the population is moving about to look at how well people were, not individuals, but how well the population was complying with restrictions. And I should say here that we're we've never been interested in tracking individuals. It's all about the bulk movements, what goes on. So we very quickly got that managed to quickly stand up someregular outputs. At one point we were reporting daily on what was happening because things were happening so quickly. And as time has gone on, I think it's fair to say that the narrative from some of those faster datasets has been broadly correct. But obviously as you get the more detailed information and more of the breakdowns, the information in, you can have a more robust, accurate measurement, not just the “well it looks like it's falling really rapidly”, or “it looks like it's coming back up again” kind of interpretation.    MILES FLETCHER  In terms of speed, the delay between data creation and data analysis is getting ever and ever shorter. How fast can this get at what point will we be able to be able to read daily readings of the economy for example, daily readings of population shift?     LOUISA NOLAN   I think that it's becoming possible. I don't think you'd ever, I don't think you would have daily GDP because there's so many elements in GDP that you couldn't collect on a daily basis. The question is, particularly around the economy: How useful is having daily outputs on the economy? If you knew GDP daily, how would that help your decision making? But for population if you know what population density and how that changes over a day that might be really useful because that will tell you something about where there’s high density areas, how people are travelling about how people are not travelling about , over COVID. And that would help with things like your local planning, with managing big events and so on, and help us to spend money more effectively because we know where people are and we've got a better and quicker understanding of where populations might be both in the short term over the timescale of a day and in the longer term.     MILES FLETCHER  You mentioned observing cows from outer space as well. I've got to ask you what that involved?    LOUISA NOLAN   Oh, counting cows, we love this. We have a data science hub that's embedded with the Foreign, Commonwealth and Development Office in East Kilbride. They focus on supporting the UK’s mission to support developing countries around the world. And one of the projects that our team is doing, our team there is doing, is counting cows. So in South Sudan, where agriculture is a much bigger percentage of GDP, a huge part of GDP for them than it is in the UK. And cattle is really important, but it's quite difficult to go out and count all the cows is a huge country. Not great roads. They've had various different issues with weather and conflict there as well. So the question was, can we get a good picture a good census of the cattle in South Sudan using satellite data? And actually, it's quite it's quite promising. We have ever better quality of satellite data, higher resolution. You can see where the camps are and you can make some estimates around the number of cows there. Getting hold of your ground truth data to check whether your estimate from spaces right is probably the hardest part of that, but it's quite exciting. And of course, if this works, what else can we do with satellite data that's helpful and means that you don't have to send individual real people out over these vast areas to count things.    MILES FLETCHER  That's operating on the global scale as well, but you've also been working on ways of minutely examining documents that are submitted to government in very large numbers and bypassing human intelligence to use artificial intelligence to interrogate those documents and draw conclusions from them.    LOUISA NOLAN   That's right. I mean, one thing government is good at is having lots of words and documents and turning those documents from data, if you like, into information and insights is a big part of what we do. So we use natural language processing to do text analysis, and we worked with the Department for International Trade on one of their big consultations, they had more than 400,000 responses. And we were able to automate that to identify themes and topics in the responses in a faster way than you can do by hand. They also covered this in the traditional ways so we were able to compare our results with the manual approach as well. Certainly the automation is faster. And I think sometimes when you've got that much information, you can get different insights, new insights from automating. But when we look at AI and approaches like that, you really want to take the human in the loop approach. So you run the things that are automated, for the bits where it makes sense, where you can find out things, you can make things go faster. But if there's something which is difficult for the AI to come to a conclusion on, that's when you bring your human in to go, oh what does that look like? Where should that sit? How should we interpret that? And it's that combination of automation, getting humans to do the bit humans are good at that's really powerful.    MILES FLETCHER  So the campus is a campus in both senses really. It's a campus and that it has projects and enterprise and things getting started up, but it's also a campus in the academic sense as well. And you're training people some of whom have no background in in these sorts of disciplines at all. Tell us about what's been achieved there.     LOUISA NOLAN   So our capability team were set a task to train 500 data scientists by March 2021. Well, we far exceeded that we trained 680 something in that time through a range of different programmes that we run. These include the MDataGov, the master's in data science for government, which we run in partnership with four universities. The graduate programme, the apprenticeship programme, face to face learning and our accelerator mentoring programme, which is brilliant. So this is open to everybody across the public sector. Pitch a project. If your project is successful, then you get for 12 weeks, you get a data science mental for one day a week to do that project and that project will be something that's important to your home department and also help the individual to build the skills as well. There's been a massive range of projects and departments who've taken part in this. I think we've had more than 250 people through the accelerator so far. It's great. So we're always looking for more mentors as well. So if this sounds interesting, always, always looking for people to help out with the mentoring.    MILES FLETCHER  And in the apprentices, you're getting people coming in from the local communities in many areas around where you're based in, in South Wales, and coming in cold in many cases with no background in working in these sort of disciplines at all.     LOUISA NOLAN   That's right. For the apprentices it's about enthusiasm and potential rather than anything that's happened before. We've had a range of people from a huge range of different backgrounds, a huge range of different ages from straight out of school all the way to people who've had several careers beforehand who've wanted to retrain. It's a brilliant way to get diversity into data science, and I'm hugely supportive of this approach. It's great.     MILES FLETCHER  And how do you go about applying then for any of these opportunities?     LOUISA NOLAN   So we advertise them, the best place to go is to look at the data science campus websites where we advertise all of our learning and development programmes. And also we talk about our projects and the other things that we're doing so you can find out all kinds of information there. For jobs and recruitment, like the recent round of recruitment for the graduate data science programme, that will be on civil service jobs, but the first place to come as the data science campus website.    MILES FLETCHER   What are the challenges that immediately lie ahead for the campus then, what are you getting your teeth into now?     LOUISA NOLAN   So I think one of our challenges is a good challenge, which is that data and data science has never been a higher priority. I think so we have a lot of asks on us. I think in four years things have changed. So four years ago, there weren't so many data science teams across government, there are more now. So we need to think, make sure that what we're offering is still the right level as other departments mature as well. I think the desire for ever faster information is not going to go away at all. So more of that, and also thinking about how we can use data, novel data and data science to support the government's big programmes like net zero and levelling up and also continuing to support our response to COVID. And thinking about what we learn from that, how we can use what we learn from that for other aspects of health as well.     MILES FLETCHER  And Will everybody be a data scientist in the future rather than just a statistician? Dare I ask?     LOUISA NOLAN   Oh, I don't know. That’s a very controversial question that. I think data science, data scientists aren't unicorns there are aspects of data science, that is a subset, or if you imagined a Venn diagram have overlaps with statistics, with operational research, with economics, a lot of economists really interested in data science and big data. But also with the digital skills as well. So overlaps with data engineering and software engineering. So my hope, my dream, I don't have a dream data science person, it’s always a team who's made up of all of those different skills. And I hope that more people will have an opportunity to build at least some of those skills, even if they don't call themselves data scientists. One of the other programmes that I'm really proud for the campus to be leading which we developed in partnership with the Number 10 delivery unit is the data senior leaders data masterclass. So this is a masterclass designed for public sector, senior leaders talking about data, why it's important, how you can use it for evidence how you can use it for evaluation, not expecting people to come out coding in Python, but having a better understanding of what's possible and what the right questions to ask are. So we rolled it out to all permanent secretaries. We're hoping to roll it out across the senior civil service. Also the fast stream and some of the future leaders development programmes across government and it's also open to senior leaders from the wider public sector as well. I'm really pleased about this because I think if we can build those skills at the top level, get people understanding what the opportunities are then that helps us build that capability, increase the number of people who can do that coding, improve efficiency and help use data better to make better decisions.    MILES FLETCHER  That’s Dr. Louisa Nolan from the ONS Data Science Campus and before that National Statistician Sir Ian Diamond. In the next episode of Statistically Speaking we turn to the economy. With the rising cost of living on everybody’s minds, how does the ONS keep tabs on inflation? Is there more to national prosperity than mere GDP? And is economic forecasting really just a way of making astrology seem respectable? Join us then. You can subscribe to new episodes of this podcast on Spotify, Apple Podcasts and all the other major podcast platforms. You can also get more information by following the @ONSFocus twitter feed. The producers of statistically speaking are Joe Ball, Elliot Cassley and Julia short. I'm Miles Fletcher, goodbye.  

Since 1801 the UK has undertaken the mammoth task of counting its entire population, transforming over the years to uncover a wealth of information about the people of our country. With all the data collected for Census 2021 our most comprehensive quality assurance programme ever is currently under way, drawing on the unique insight and expertise of local authorities across England and Wales to help us produce the best possible statistics for every local area. With results expected in early summer, Statistically Speaking meets the people who ran the first digital-by-default census during the pandemic to find out how it went and what the results will able tell us. Transcript: MILES FLETCHER Welcome to ‘Statistically Speaking’ the podcast where numbers talk and we talk to the people behind them. This month we peek behind the scenes of one of the UK’s biggest mass participation events, the Census.  Almost every ten years since 1801 the UK has undertaken the massive task of counting its entire population. But what began as a headcount to measure population growth has gradually transformed over the years to add a wealth of information about all of the people in our country.  So now, with all the forms collected, a very large programme of quality assurance is going on and that means taking data from an array of alternative sources, information gathered by the government for other purposes, to see how far that corroborates the picture that's emerging from the census forms. And also for the first time this year we're drawing a unique insight and expertise of councils across England and Wales as to use their local knowledge to help us produce the best possible statistics for every area.  Taking the further evidence gathered from those 250 organisations into account, we now aim to publish the first results in early summer 2022. However, some releases of early data have already helped to shed light on the effects of the pandemic, and more recently, the response to the Russian invasion of Ukraine.  Today I'm joined by Pete Benton, one of the people chiefly responsible for running the first ‘digital by default’ census during the pandemic, and Sanjay Jagatia one of our vital Census Community Advisors.  Pete Benton, the England and Wales census, it's the largest statistical operation certainly that any government has to undertake, and it's sometimes described as the largest regular peacetime operation that UK government does. But just give us a sense of the scale of the whole thing and what's involved in numbers. PETE BENTON Well, the simplest way to think about it is we're asking everybody, every household in the country, to do something in the same way on the same day. That's quite a challenge. You know, people compare running a census with standing up the London Olympics. That’s a big job but you don't have to get everybody to take part. And in simple numbers, there are about 25 million addresses in England and Wales and we need to get a response from everybody. MILES FLETCHER The ONS, it's a relatively small organisation for a Herculean task like this. It isn't a case of everybody in the ONS downing tools for a few weeks, is it? And this time around we're measuring COVID and the economic impact and all of that. So, who are the census people, where do they come from, and how long do they stay with us? PETE BENTON Well, it really does take us 10 years to plan every census. The 2021 census - I actually started with a team in June 2011, just after we'd done the 2011 census. Now, the first question wasn't how are we going to do the next one? The first question was, do we need another one or can we get the information that is so desperately needed about the size of the population from data sets that already exist? So, we spent three years looking at questions, specifically after the 2011 census, and then in about 2014 came fairly firmly to the conclusion that we do need a census in 2021. And there were seven years-worth of efforts and some people were still around from 2011. There were even some from 2001, one or two people who'd even been part of the 1981 census so you get a little bit of corporate memory, but most people are new when each census comes along. We have a small team to start with. And then it just grows. And in particular, in the last year or two, you fill up the office with the people that are going to run the operation. MILES FLETCHER As well as the people in the office, you've got to organise this huge army of people, this ‘fieldforce’, who actually, as you say, go out and knock on doors. PETE BENTON You're right. When I joined back in the 2001 census, just after that, that census took about 70,000 staff. And the census before that took over 100,000. By the time we got to 2011, with advances in technology able to support people in different ways, we brought that down to 35,000 staff, and for the 2021 census it was under 20,000. So actually, we’ve become better and more efficient as technology enables us to change the way we do things. MILES FLETCHER Now there was less activity on the doorstep perhaps this time of course because for the first time we were trying to get everybody, if they could, to do it online. What were the challenges of that particularly? PETE BENTON Well, interestingly, it’s always been a self-completion job, or at least certainly for recent decades. You get a paper questionnaire come through your door, you fill it in and you give it back or post it back.  The big difference this time was that we wanted the vast majority of people to do it online. There was no online option for 2011. By the time we'd given everybody a paper questionnaire, they mostly did it on paper. 16% in 2011 did it online. But for 2021 we’re at 89% of households who completed the census having done it online, and 11% having done it on paper. Now that's quite a shift in a decade and so far, I think that's the highest online percentage of any census around the world. There are a few going on at the moment. Australia's has only recently happened and we're still waiting to hear how theirs went. But that shift to doing online actually genuinely for most of the population did make it quicker and easier. And for us, in ONS, because it's all electronic, we can see immediately when every household has responded and can see those that still need some further help. MILES FLETCHER The technology on the day. It was smooth, it was efficient? PETE BENTON It was fabulous. So of course we thought long and hard about how big might the peak actually be and we scaled the system to be able to cope with our predicted online demand. And we've actually worked very, very close with our estimates.  At the peak we had 60,000 submissions in a 10 minute period at near lunchtime on census day. And that's the submissions, but when you think that people are looking at our website and they're going through every question, the load on the website was quite phenomenal.  During that peak period we had 30,000 requests per second for information to our website, whether it was to serve the next question on the questionnaire, or to get a bit of extra information about the census. And because we built it in the cloud that just scaled naturally and easily.  We worked with the cloud providers to make sure that we understood how to make things dynamically scale according to the numbers of users, and it worked absolutely seamlessly. You can imagine there were a few people biting their nails in the days running up to it, with something quite that big, but on the day it went without a blink. MILES FLETCHER Now there’s always a bit of a PR push to let everybody know that the Census is taking place. This time around we had some new events and happenings taking place. Do you want to just talk us through how we drew people's attention to it, and got it onto the media and into the news? PETE BENTON It was a mixture of things. I mean, every address got a postcard through the door two or three weeks before to say “the census is coming, watch out for it”. Every address got a letter through the door a bit later to say “census is coming, here's your access code”. So, every address had something that said it's coming.  But sitting around that was a huge campaign. There were TV adverts, there were radio adverts. There was an awful lot of stuff just in the news because we were pushing it out there and people got behind it. But we also for the first time had 300 local staff, six months before the census, just working on local community engagement, getting the word out. We worked really closely with local authorities to use all of their local networks to promote the census to every local group so that everybody knew that it was coming, and also just how much it mattered for their community to be counted. Because if they weren't counted they wouldn't be in the numbers, and services couldn't be planned to meet their needs - services like the NHS and school places and transport - these things all depend on the number of people in a local area. That campaign was essential to get the response rates up. MILES FLETCHER And it's the campaign that has to reach the parts that other campaigns can't reach because, when you're trying to reach every single household in the country, there's always quite a proportion you cannot reach through the media. Who are those people, and how did we get them particularly? PETE BENTON So, we translated all of our materials into 50 different languages. And we had specific adverts in certain languages on the radio and on the telly, and we were tailoring the content and tailoring the networks we were using to get the broadest reach we possibly could. And we estimate that after census day, well over 95% of people were aware of the census and knew that it was coming. It was incredibly successful and it translated into over 97% occupied households actually filling in a census, because only one person for each address needs to do that. So you don't have to have every person knowing that it's coming but at least have one person from every household. MILES FLETCHER And that engagement of course comes to a head as Census Day approaches. We have buildings being lit up in the census colour of purple; we had mentions on soap operas; you're on the BBC One Show as well, banging the drum for the Census. And what was fascinating is that you could see in real time, because so many responses were coming in online, the completion rates were being boosted by those appearances as they took place. PETE BENTON Absolutely. We had real time dashboards telling us both how many people were on our website and how many were completing the questionnaire at any given point in time, and you genuinely could see spikes where the number of people on our website jumped fivefold in a particular minute when the census was mentioned on Gogglebox. And you saw peaks when the census was talked about in EastEnders and on The One Show and BBC News, and then when the TV advert went out on the Saturday night before census day, you could see it in the Ant and Dec broadcast. So through the spikes you could see the impact of the advertising that we did. MILES FLETCHER So, you could see some of these early returns going well, but what's it like to be in charge and responsible for that huge operation on the morning of census day itself? Does it feel like Christmas day or do you wake with a sense of trepidation about whether or not it's all gonna work? PETE BENTON Well, by the time you get to Census Day, interestingly, you kind of have a sense of how it's going because the letters land on every doorstep three weeks before Census day. So you've got a sense of how many people have been responding, and what times of day they've been responding, over previous days and previous weekends.  And interestingly, we had the weekend profile from the two previous weekends before census weekend and we could see on the Saturday and on the Sunday what time of day the most responses came in. And it was typically about 11 or 12 o'clock.  So by 11 o'clock on the Sunday of census day we knew that was the peak hour probably, from what we've seen the week before.  We knew by seven or eight o'clock how big that peak was likely to be, because on previous weekend days we'd seen that eight o'clock peak was about a quarter of what the peak was going to be at lunchtime. I can't remember the exact numbers, but I was looking at seven or eight in the morning to try and predict “how high is the peak?” and what's the total likely to be. And by the time we got to 10 o'clock I think we were comfortable that the peak looked like it would be manageable within our projections and it certainly was. MILES FLETCHER And that continued then according to your expectations during the day. Did you have a sense then, come the end of that day, just how many people had completed and whether you were on course for success? PETE BENTON Yeah, we could see that we were ahead of what we'd expected at that point. And that is a census-takers dream because you can imagine knowing that you've got this fixed window as a census day. It's a fixed day, there's a period of letters that are going to come out and remind those that haven't responded after the census date, and then a fixed period of field staff. And you know you're on tenterhooks waiting to see whether the response is going to come in quick enough and be big enough. And by the end of the Census Day, we could see actually things were going well and at that point, you can breathe and say, “Okay, we're going to be alright”, you know. When things go wrong it can be horrible. There are stories from around the world of websites breaking on census day and front page news for weeks as the public follow this kind of scenario unfolding, and you know that God willing, we won't end up there, but you know that it's possible and so as you get towards the census there's both nerves and excitement kicking in. MILES FLETCHER Okay, so by the end of census day you've got a pretty good picture of how well you're doing, but you know that not every household can possibly have completed it. What do you do next? How do you pull in those remaining households that haven't taken part? PETE BENTON So there's probably three big things that we do. We continue the publicity campaign, we look for the opportunities to get on the radio and on the telly and just talk about how well it's gone. We put press releases out so the conversation continues, and that was really successful.  But then we can see of course, which addresses have responded and which haven't. There's a slight lag in the ones that have come back as paper questionnaires - it takes a while for those to be receipted. But nonetheless, we can see which addresses haven't responded, and at that point we send a reminder letter. The most effective thing we can do is send a letter - it would cost an awful lot more to send a person out on the street.  Firstly, we try and get people to respond without needing a reminder through all that publicity campaign. Secondly, we send reminder letters and people can get three or four over a period of three or four weeks. And then after about a week, that's when in earnest we start sending out field support staff to go knock on the door and say “we see you haven't done the census yet, can we help?” And most people would say “oh, I've done it” or “I’m about to do it”, and they would genuinely get on and do it. But there were some that needed a few more reminders than that. But eventually we could see that those letters were working and that the field responses were working.  And of course there was also the option for people to fill it in on telephone, if they couldn't get online weren't able to fill it in on paper, but could do it more easily over the phone. And so by making multiple options available and making sure they were well promoted, we got a fabulous response. MILES FLETCHER There was an issue wasn't there with some people who thought they completed it, but hadn’t pressed ‘Submit’, and were then getting chased up. PETE BENTON That's right, the Census is a legal document and you actually have to say “to the best of my knowledge and belief this is a true reflection of my household” and press the submit button. And there were a few people who had got to the end, thought they've done the job, but hadn't pressed ‘Submit’. And so actually, they ended up getting a letter that was very specifically worded that said “we can see you've started the census online, but you haven't yet pressed ‘Submit’ would you like to get back and finish it off?” And we saw a good response to that as well.  I'll let you into a little secret. I actually got one of those letters. It wasn't because I had forgotten to press ‘submit’. It was because my kids actually weren't at home on census day. Two of them are out of the country. And I was debating with them. When are you coming home and are you to be counted in the census because there are some quite precise rules. Because if you're out of the country for more than 12 months, you shouldn't be counted, but if you’re out of the country for less than 12 months you should. So we were just discussing “when are you going to be home? Do you think you'd be home within 12 months?” They said yes, but we didn't quite get there by Census day. I’d filled in my bits, my wife had done hers, as had my stepdaughter, but I was just waiting for two bits from my other kids. And it was fabulous that they could using our access code from our household which I shared securely with them via a secure link. They could go in and fill in their details, pass it back to me and eventually I pressed ‘submit’ a few days after census day. MILES FLETCHER How difficult was the decision to go ahead with this census, despite all the years of planning? How difficult was it to press the button and go ahead despite the fact that there was a pandemic still in full swing and the country was still in effective lockdown? PETE BENTON Well, you can imagine that was one of the biggest decisions that we've made. And in principle there were essentially two questions that we asked. The first was “can we keep the public safe? And can we keep our field staff safe?” And the second was, “can we get good statistics?” And you can gather from the fact that we went ahead that our answer to both of those questions was “yes, we can keep people safe and we can produce good statistics” but we spent a lot of time looking into that and we actually changed a fair bit of the operation.  All of our recruitment and training for our field staff moved to being online where sometimes we might have gone into somebody's home to give them support, we were very clearly not going to be going into anybody's home. We kept two metres distance, we kept masks on at any point where we did do a field visit, and even doing those field visits there’s a big decision to go ahead and continue. We had options just to use letters to remind people. But we went ahead and we got good statistics.  We had to give some extra guidance here and there for certain questions. When we asked “Where do you normally work from, at home or in the office?” We always ask that because many people always have worked at home. But people we saw as we tested some of those things out were kind of thinking well, “what do you mean, do you mean now or do you mean prior to the pandemic?” So, we gave some guidance on a few questions to say answer now, as it is now. So that guidance was clear and straightforward.  But there will be some interesting artefacts that we find from this census. So one of the questions the census asks is “Where do you live? Where do you work? And how do you travel to work by car, by train or by bike or by walking?” And of course in the middle of a pandemic, most people, or many people, weren’t travelling to work. Post-pandemic we're seeing more people travelling to work, albeit they will never get back to the levels before. So the census itself will show not many people travelling actually, and the census is used for planning transport. How wide do the roads need to be? How many trains do we need? That's all based on census information. And so we're going to need to find ways to update that information after the census for some of those things. MILES FLETCHER So the operation benefited hugely as it turned out, from having what was literally a captive audience – people were at home and ready to take part, as it turned out in large numbers. But just how big a problem is it that it was done in those unusual circumstances that you mentioned? Indeed, might it even be necessary to do one again after a few years, rather than wait another 10? PETE BENTON Well, actually, when you think about it, it was critical that we did it at that time. We just left the European Union and we were at the heart of the pandemic, and it gives us a fabulous baseline. We know that the population will continue to change as we adjust to a new normal, whatever that might be - no one knows what that's going to look like.  So having that baseline to say where were we, and then every year to refresh those statistics and say: How has the population changed? How has the way we work changed? How has the kinds of jobs that we're now doing changed? And how do we travel to work - how has that changed?  So what we're now planning is frequent updates to our statistics, both how many people are in a local area and what types of people are in a local area, using all kinds of new information sources to chart out the change post pandemic and post Brexit baseline. MILES FLETCHER So it's a successful operation. People were convinced about the need to take part. They took part in very large numbers online. Just how successful do you think it was then? PETE BENTON We estimate that we got a response from over 97% occupied households. Now that is quite something. We set ourselves a target of covering 94% of the whole population in the census responses, but that is just the first step.  You know, knowing how many addresses have responded is the beginning. But different addresses have different sizes. Some have more people in than others. And it might be that some of the addresses that didn't respond, the few, were either larger or smaller than the average address. So we don't know yet what percentage of people we covered and there are some fairly clever processes that we go through to actually work out who we’ve missed. MILES FLETCHER In historic terms, how successful is a 97% household completion rate? PETE BENTON Well, in 2011 we estimate that we hit 94%, and something similar in 2001. So 97% is pretty good. But actually we've got a bit more information this time about those vacant addresses than we would have had in the past. In the past, all the record books that the collectors used were on paper. For the first time in 2021 all the field staff had a mobile phone with an app on it that gave them their workload and they could record the outcome of every address that they visited. And so, within a moment, we knew centrally every address that the field had said “this one is vacant”.  We've never had during the operation that kind of information before, we've always waited till the end and we've always talked about what percentage of the population we've covered. So in a sense there isn't a comparable figure, the comparable figure will be ‘what percentage of people did we count’.  But nonetheless we're pretty sure that 97% is good going. Of course, in 1801 we have no idea how many addresses were covered. We've got the results, we know something about how they did it, but they didn't have computers, they didn't have address lists. They didn't have extensive records. A lot of it was managed by people just keeping track locally of what was going on.  So we're getting to a world where information becomes more and more finely detailed as we go through running these operations MILES FLETCHER And to get a better handle on what you don't know as well as what you do know. PETE BENTON Absolutely. And in the last three censuses, we've actually made quite a big step in how we assess that total coverage of the population.  To plan public services you need to know about everybody, every different community group, every age group in every part of the country. As you can imagine, doing a census, there are some groups that are more willing to respond than others. Older people tend to be more diligent in completing forms, certainly more diligent than students and young men or busy young families. So we know that sometimes we miss people because they're busy, and they just don't quite get the census done, and we make adjustments for that. But what we don't want to do is just add a percentage of all age groups. We want to assess who have we got a high response rate from, and who have we got a lower response rate from, and what adjustments do we need to make to our statistics so that the results do the very best at representing the whole population, even if we didn't count every single one of them.  And there's a technique we use called ‘capture / recapture’, and it's used for wildlife if you want to count how many ladybirds there are on an island or how many fish there are in a pond or even how many taxis there are driving the streets of London. There's a technique you can use, and then we apply it to the census. So let me talk you through that step by step. And if you're really interested in this, there's a little article online. It's called Trapped Catfish and Roach, the beginner's guide to census population estimates. If you Google that it's only a few pages long and all you need to read is the first page but I'll explain it to you now.  So, you get the idea. Just supposing you've got a pond in your garden and you'd like to know how many fish are in it, and you could drain it obviously, but that's a lot of work and it wouldn't do the fish much good. So instead you catch as many as you can, and supposing on the first day you catch 100 fish, then you very carefully put a little tag on them. Then you put them back in your pond. You let them all mix up and you go back the next day and you go fishing again, and this time you catch 50. And you find that 25 already have one of your tags on them. How many fish out there in your pond? MILES FLETCHER I don't know. I’ll blunder a guess and say 400. PETE BENTON So what you do know: you saw 100 Fish on day one. And on day two, you saw another 25 that didn't have a tag, so at least 125 are in the pond. You can be sure of that. But you can guess there's going to be more swimming around that you've never seen.  But the interesting thing that you learn on day two is that half the fish in the pond probably have a tag because you caught 50, 25 had a tag - half of them. So you can kind of have a guess that maybe on day one you tagged half the fish. Given that you tagged 100 that means there are probably around about 200 in the pond in total.  And you’d be right, give or take a few. And the question is give or take how many? And the interesting thing is the more you catch on day one and the more you catch on day two, the more confident you can be.  So we catch as many as we can in the census - that 97% that I told you about is our first day and we don't put a red tag on people because everybody's got a name and an address, and a date of birth, and the sex, and we know that from the census returns. So then we go out again about six weeks after the census and rather than ask people to fill the form in we say will you just do a quick interview with me? And we asked them their subset of the census questions again. Then we do it just in 1% of postcodes, and we list all the addresses blind we don't give them an address list this time. We say here's a boundary on a map. Here's a postcode. Go and list the addresses and go and interview as many people as you can. And they've got names and addresses, and sex, and date of birth. And we literally match the two together, and we go to about 300,000 addresses when we do that. And in doing that we can do those sums. How many do we catch first time? How many do we catch second time? And we can estimate the total but because we know everybody's age and sex we can see how it varies for different age groups. And we also ask ethnicity and we see how it varies for different ethnic groups. And we also can see different housing types. So big houses, small houses, and we break it all up into those subgroups, do the estimating and then add it all up. And that tells us in total what percentage of people we've missed in those 1% of postcodes, where we did that second count.  And then we take that information and we kind of generalise to the other 99% of postcodes where we didn't do the second count and with a whole bunch of fancy maths, we can estimate the total population. MILES FLETCHER And that is how you fill in the missing 3% of households. PETE BENTON Exactly. And we pride ourselves on not just doing that nationally, but getting it so that right down at the small areas of the country. All the totals add up to the total number of people living there as best we can estimate it.  So, a lot of work. It takes us a while. And interestingly, we're the only country in the world that attempts to do that process before publishing the census results. Other countries will typically publish the raw count, accepting they've missed a few, and then they'll spend the next year or so looking through the data and adjusting their overall totals but they don't adjust the small area data in the same way that we do.  MILES FLETCHER So we're at the point now where all the data has been gathered. ONS has gone away to go analyse it all and we have the wait for the final published statistics, including of course the most important population estimates of how many people are in the country and where they live. PETE BENTON So, the first job is not just to collect the stuff that came back online, but also to scan every response that did come back on paper. Whilst it was only about 11% of addresses, that still amounts to somewhere near 3 million paper questionnaires. Each one of those is 30 pages long - it takes a while to scan all of that and to catch the data and we do it with computers using optical text recognition. They're all in there, very secure, confidential processing operation.  So it took us till about August to get all of that data captured. Then we put it in the mix and we merge the whole lot together. And you know, the interesting thing is you find some houses that have responded twice. So they've sent you a paper return and somebody else has sent you an online return. And even sometimes, people are counted in more than one location different people in different addresses. Parents count kids. Like mine. Parents of divorced families may well both count their kids, so we do a check next of any duplicates and we remove the duplicates. And then sometimes people do give us some unusual answers, like, you know, children who are three years old and they're married or working in a factory and we do our very best to try and tidy up some of that so that at least what we're publishing is consistent and, you know, we'll kind of say for three you're probably not married and fix some of that. Sometimes people do skip a question and we'll do our best to estimate. Based on their near neighbours, what might the answer have been if they didn't fill in the question about what kind of heating they have in their house? If 99% of the houses around them have got gas central heating, we'll take a punt and say it is probably gas. So you get better statistics that way.  So, there's a bunch of tidying up to do. And then there's the work to estimate how many people we've missed by linking it up with our Census coverage survey data. That in itself takes another while and then our estimates come out. And then the next job is to say okay, do those estimates make sense?  And we compare it with other sources for how many people have got a National Insurance number, how many people are registered with a doctor, and do our results sit comfortably with those other sources. So, a lot of work to make sure the results are plausible and make sense to when they come out. They're as valuable as they can possibly be.  MILES FLETCHER So this huge sense checking operation takes part so that the statistics as you say are as valuable as can possibly be. What can we expect to see first then, is everything going to be released?  PETE BENTON So the first thing that we will do is publish that size of the population. By age group and sex for every local authority in the country, so that every local authority can see how many people are here and they can plan on the school places they need, and how many houses might need to be built. And then every couple of weeks after that, we will keep releasing more and more detail like how many people have got a job, what kinds of jobs people do, how's that vary by ethnic group. And then we will publish something like 5 billion numbers, 5 billion statistics, and that takes us a while to get it all quality assured, to get it all published. But for the first time we will also make available a flexible table builder so people can take a look and say, well, could you give me a count of how many people are this age and working in this kind of profession, who are of this ethnic group, who are gay or whose gender is different from what was assigned at birth, and people can actually produce their own statistics. Now we double check to make sure there's nothing that's being published that has any risk of identifying a person, because you've got small numbers. But that flexible table builder will mean people can answer some of the questions that might have taken longer in the past more quickly.  MILES FLETCHER Billions of data points. How do you make it so detailed to be so very useful, and yet protect anonymity? PETE BENTON Well, we spent a long time making sure the questions work in the first place so that when people see this question, they're not answering what they think we're asking. They're answering what we're actually asking.  But then on top of that, there's a lot we do to make sure that when you see a table that has got small numbers in it, and you might think “oh, that's Joe that lives up the street, oh I’ve just found out that he works in the clinical profession” say, well, we just don't publish those statistics for one thing. We don't publish data that is that detailed on all topics so that you know people could find that out. But there's also some sophisticated methods that we call ‘statistical disclosure control’ – world leading methods, actually. That means that when you look at a given table, you can't be confident that a number that you see actually is absolutely correct.  In the totals, the numbers are right. But if there are some fairly unique people with unusual characteristics that would stand out in a table, interestingly, we’ll often swap them with a household somewhere else. We will take one record and literally move it somewhere else, and swap somebody else back so that you don't know for sure who's there.  And then even when we publish the numbers at the end, sometimes we’ll change a number too. If there's a count of two people we’ll change it and make it a bit bigger or a bit smaller and we can do that to any particular number in any table. And we've got some really world leading methods to help us do that.  So when you look at the numbers, they're accurate, they give you a good picture in total of what's going on nationally and in a local area, but you can't identify any individual with any kind of confidence.  MILES FLETCHER So there is a very great deal more to anonymity than simply withholding people's names and addresses. PETE BENTON Absolutely. And in a world with more and more data, these methods get more and more important. MILES FLETCHER The big question, of course, is whether that was the last census of its kind that we're going to see in England and Wales. PETE BENTON Well, I wish I could answer that question today. It's certainly our intention. We are working as hard as we can to find new ways of counting the population, using data that exists in government. How many people are getting benefits? How many people are paying taxes? And can we join that information together to get a good clear, detailed picture of local communities. And we're making really good progress, but we're not going to make a decision until we've been able to compare the results of our alternative new methods with the results from the 2021 census. So, we'll do that and come 2023 we'll make a recommendation - do we have another census or don’t we? MILES FLETCHER Pete Benton – thanks very much. SANJAY JAGATIA My name is Sanjay Jagatia. I'm actually based in Coventry. As part of my voluntary work, I'm also the chair of the Hindu Think Tank UK, which is an umbrella organisation for the Hindu community across the country - almost 1.5 million Hindus across the country from the last census. And then also the Vice Chair of the organisation of people of Asian origin in Britain. And it was through that that I felt that you know, I wanted to have the Indian community being represented as part of census 2021. And when I saw the advert come through, I thought this was an excellent opportunity for me to personally do whatever I can to encourage as many from the Indian community to take part in census 2021. MILES FLETCHER You’ve told us already that you thought that working for the census was a life changing experience for you. Tell us about how it has changed things for you?  SANJAY JAGATIA I think for me it was life changing because I was one of the sceptics initially about how census data is used and what benefit, more than anything else, what benefit does it have on me as an individual and as me representing my community? What benefit has it had before?  I hadn't noticed and I hadn't realised the enormity of the whole process and how important it is, not just for us as communities, but how local authorities and how everybody else will use that data. So, we had to be counted. And that for me was life changing.  It was also life changing to see people from the age of 18 to 99 in some cases, wanting to be part of this. And the enthusiasm that has built for the first three, four months coming up to census - that for me was really, really important because I haven't seen that engagement ever before in my community for any issue that's happened. Even when you look at voting days, election days and all the other things that happen, that enthusiasm was not there as much as it was on this occasion to be part of census. MILES FLETCHER And what does an engagement manager do to make sure that happens, that people do get themselves covered in the census? How do you go about that work?  SANJAY JAGATIA When we first started, I did research in the area of all the various Indian community organisations, key individuals, people who had a large social media following as well, and started to engage with them initially because without them, I knew that my work would have been very, very hard to be able to reach their communities and their membership that they had.  So that piece of work that we did right at the beginning of the census, which was a three week period of researching the entire area to find out where people were, and who the key individuals were, that we can actually engage with the census. And what I did went a little bit further and I identified individuals who we made census champions - people who were able to work with me right throughout the period of the six months of the census. MILES FLETCHER How did you persuade them that championing census was a worthwhile thing for them to do? SANJAY JAGATIA I think you know that the previous census 2011 and in Kenya prior to that, it was clearly evident that we saw that the Indian community’s engagement was very, very little compared to other groups and minority groups as well. So, this was a key area for me to be able to say you had your opportunity or we have our opportunity of having our voice heard, you know, whether it was roads, transport, education, and what may be available for our communities in our local authority areas.  And I think having examples of how other communities have actually used the ONS Census data previously for their faiths and their communities was a really good way for me to be able to engage with my own community to encourage them to take part in the census.  MILES FLETCHER What do you think it was that was preventing your audience from previously taking part? Was it just a lack of awareness?  SANJAY JAGATIA I think the awareness this time round for Census 2021, in my opinion from my community, there was a lot more awareness a lot earlier. And I think that was because of the focus group meetings that were held with key individuals from each community in each faith. And I think back then it started to filter down to communities at least six, seven months in advance of Census happening.  And I think from my point of view, I think it was a lack of awareness of census and how important census can be for each individual and I think that's why there was a low uptake on Census previously.  But on top of that, as well, I think that there is an area where we have cultural differences, language differences as well. And I think that that was key, that a lot of information previously was very much in a mainstream English language, which was sometimes very difficult for those within the community who are elderly to actually understand that.  MILES FLETCHER And did you just target areas where there were known to be lots of people with Indian heritage? Or did you seek to look at some areas, or identify some areas, that were perhaps less well known?  SANJAY JAGATIA Yeah, I mean, to be honest with you, from my personal point of view, I wanted to have a look at those areas where there was a low uptake before, to try and see how I can actually engage them a lot earlier than those who I knew that there was larger, you know, quorums of people from the community. So my initial stages were actually looking at those areas where there was a low uptake previously.  MILES FLETCHER So you're signed up, you've got census champions, you've got a mission to go out and identify those areas where we could engage Indians, people of Indian heritage, a specific community with the census. Tell us how it went out there on the road, on the doorstep, on the airwaves. How did it go?  SANJAY JAGATIA Yeah, I mean, to be honest with you, right from the beginning, in October, November time, when I was recruited for the role, it was very daunting. You know, because we were in a major pandemic. We were in lockdown at the time and I was thinking to myself, as well as my other colleagues from other areas that how on earth are we going to engage with people because it's going to be virtual.  So, it was daunting to begin with. But you know, when I look at it now , we had so much support from the ONS where we were able to have all of our questions answered, the regular meetings that we had, the updates that we had as well, which then allowed me to start to work with the key champions, also the key individuals that were going to be working with myself and started to put together items and articles that they could use on social media, through their E newsletters, and trying to capitalise on what they were doing already, because they were also in a COVID period and they were engaging with their communities on a regular basis.  So, I then asked to be part of any communication that they were making to their communities and regularly feeding them information about the census that is coming. It's 10 days away, it is here now. You know, these are the information that you can actually go on and do online.  I was very, very fortunate that throughout my period of the engagement, I conducted over 188 Zoom calls and these calls ranged from anything from 10 people on the Zoom call to some cases, over 800, 900 individuals. Along with that there was you know, where we got temples involved. So I had a zoom call with just temple heads, you know, the President and the Secretary. So that was something that I was able to do and it really, really proved worthwhile for me.  MILES FLETCHER So, because of lockdown and the pandemic, and all the uncertainty of that, you had to go electronic and run down the streets to get the right people in front of their laptops.  SANJAY JAGATIA Absolutely. And I think if I look back at it today, I really don't think - and I honestly believe this - I don't think that I would have had the success that I had in Coventry had it been just face to face engagement. What was daunting to start off with actually proved to be so beneficial to be able to have that opportunity of reaching more people at the same time. You know, I was thinking of holding meetings in community centres and in places of worship and you know that you'd get 10 / 12 people coming to those any one time. It's difficult to drag people out of their homes to come for a meeting to talk to them about something like Census, but the fact that they were able to actually engage with myself, and me to engage with them in the comfort of their own homes was a fantastic opportunity.  MILES FLETCHER What sort of reservations did you encounter that people might have had about taking part in this Census? Perhaps of dealing with officialdom and handing over information to officialdom, perhaps? How did you how did you overcome those?  SANJAY JAGATIA I think that the biggest barriers that I had right from the beginning was that even though the ONS wasn't a governmental department as such, people felt that the information that they were going to be giving may have an impact on their benefits and their rent and all sorts of different issues that they may have personally, you know, whether they were illegally living in the UK, for example, and I think that was a reservation to start off with. The amount of information that was being asked initially, there was this fear about letting that information go out into the public domain.  Having said that, once we started to get the dummy or the draft questionnaires that we were going to get people to fill in. I think the whole spectrum changed because it wasn't as in-depth information that they were thinking initially that they had to provide. MILES FLETCHER And of course it's an important message at every census time that all of the information you share, all the personal information that you share, of course, remains absolutely confidential for a very long time indeed. Do you think the people you were dealing with were perhaps more receptive to hearing that message from you perhaps as someone with status in the in the Indian community? SANJAY JAGATIA Yeah, I mean, I think one of the key things there is that it wasn't just myself but the idea of engaging community leaders who they have a very good link with. That was a key thing for me that they listened to the community leaders and the key influencers and then their reservations were sort of somewhat limited thereafter.  MILES FLETCHER Overall then share with us if you would some of the most rewarding bits of this experience. What would you chalk up as your biggest successes and most rewarding experiences?  SANJAY JAGATIA I think the biggest thing for me was actually census day, you know where I had zoom meetings right from 7:30 in the morning, right the way till 11 o'clock at night, and the urgency in people wanting to make sure that they take part in the census on that one particular day. Even though they had the opportunity a week before to start this, it was census day itself and the urgency of “yes, I want to have my vote. I want to have my say. I want to be able to say what I want to do going forward in the census”.  I think that for me, that particular day was fantastic. Not just online but to be able to go out and help people fill out their census form as well going out into the city centre, going out into some of the areas where lockdown restrictions slightly had been lifted at that time. And that was a really, really a brilliant occasion for me.  MILES FLETCHER I'm sure Sanjay a lot of the credit for that then rests with you. The proof of the pudding will come where we see the results of course, but in the meantime, thank you very much for joining us today and thank you very much for everything you did for 2021 census. Thanks to Pete Benton and Sanjay Jagatia.  In the next episode of ‘statistically speaking’, we're joined by the National Statistician and the chief data scientist at the ONS data science campus. We hear from them how a data revolution and the fight against COVID changed UK stats forever, how we kept the numbers coming at a time of crisis, and how ONS statisticians are using faster forms of data to gain ever clearer new insights. You can subscribe to new episodes of this podcast on Spotify, Apple podcasts and all the other major podcast platforms. You can also get more information by following the @ONSfocus Twitter feed. The producers of ‘Statistically Speaking’ are Elliot Cassley and Julia Short.  I'm Miles Fletcher. Goodbye ENDS.  

Since April 2020, the Coronavirus (COVID-19) Infection Survey has provided vital weekly snapshots of the level of SARS-CoV-2 virus circulating within the community. We’re joined by three central figures in the project, Ruth Studley, Tina Thomas and Professor Sarah Walker, for the inside story on one of ONS’s most ambitious surveys, set up in a matter of weeks as the pandemic took hold. (This episode was recorded in September 2021, before the emergence of the Omicron variant)   Transcript:  Miles Fletcher, Head of Media and Public Relations at the ONS Numbers, numbers everywhere, but here we’ll take some time to think about where they come from what they mean, and where they're going. Welcome then to the first episode of statistically speaking the new official podcast from the UK’s Office for National Statistics. In this series the nation's number crunchers, as some people still insist on calling them, chew the fat and spill the beans on the stories behind the stats. Lately, they've been making headlines, some would say ruling our lives, like never before. I'm Miles Fletcher and in this first episode we'll be looking at how millions of swab tests and finger prick blood tests allowed the Office for National Statistics and its partners to track the progress of COVID-19 across the UK. During the pandemic, the COVID infection survey has proved a vital source of regular data on Coronavirus infections, antibodies and symptoms. We'll hear why this huge study was needed in the first place, how it was set up in double quick time and what it's told us about the virus and its human impacts, and why it remains important now. Joining us are three central figures in the project: Tina Thomas, who runs the survey operation itself, leading a force of thousands of study workers out gathering data in the field; Ruth Studley Head of Analysis for the ONS, whose job it is to turn those test results into fast statistical estimates that we hear about in the news every week; and from the University of Oxford, the chief investigator and academic lead of the infection survey, Professor Sarah Walker. Sarah, to start with you first, how did this study get underway? And well, why was it needed in the first place? Professor Sarah Walker, Chief Investigator and Academic Lead for the COVID-19 Infection Survey So it was back in April 2020, when a lot of people had, you know, been sick with COVID in the first wave. But we really didn't know how many because at that point, we didn't have the PCR tests that are done in the laboratories, we didn't have the tests on a stick, the lateral flow test that lots of people do before going to school or work. And we really have no idea how many people had actually already had COVID. And at the time, there was actually a hope that we might even be close to herd immunity then. And so initially, in the middle of April, the infection survey was first of all a study looking for antibodies in the blood. And the initial plan was to sample just around a thousand households in the first month, then a further thousand households a month for a year to just find out how many people had had COVID already. But over literally the course of two or three days from the 17th to the 19th of April, we realized that actually, we didn't know so much more, in particular about how many people were infected without having any symptoms, how many people were passing it on to other people in their household, how many children were infected. And very rapidly, the survey increased to sampling over 11,000 households in the first month with an initial plan to then resample another 11,000 households a month for a year. Miles Fletcher  Quite simply, you needed to have that representative sample of the whole population, it wasn't enough just to rely on people coming forward who suspected they had COVID. Sarah Walker Well, exactly, because what we cared about was what was really going on in the community. And it's well known that people who come forward for testing tend not to represent their communities completely. And so this was why initially, just because we had to get going so fast, we did actually approach at random people who had been in previous ONS surveys and said they would be interested in taking part in future research. But very quickly, we moved to just sampling from addresses. So, to really get a completely random sample of people living in private households across the UK. Miles Fletcher  And how did that connection with the ONS come about? Because it's a new departure for the ONS, we normally measure the economy and migration and so forth, but not medical testing. So how did that partnership get started? Sarah Walker So, I really think it was a case of everybody just working as hard as they could together to make this happen fast. And what ONS do have huge experience with is these very large population representative sampling frames, and they also had access to this databank of people who had been randomly selected for previous surveys and who had said they would be interested in taking part. It's a huge field operation and obviously ONS has got huge expertise in that. So, I think they were in many ways, you know, the obvious partner to really take it on. And it was a huge collaborative effort between the Department for Health and Social Care as well as the University of Oxford and ONS. Miles Fletcher  And this all had to happen in a fraction of the time that's normally available to plan a big survey, for example a census, and it was almost on that sort of scale. You need every community, every age group or socio demographic group represented in that massive sample. All this had to happen in a matter of a few days to start with to get the first estimates. Sarah Walker We wrote the first draft of the protocol on Friday the 17th of April, we submitted it for ethical approval on Monday the 20th of April. So that's just four days later, during which time we had gone through three major changes in scope and size. It was approved on Tuesday the 21st of April, we recruited our first participant on Sunday, the 26th. So literally ten days after the first draft, and we published our first estimates two weeks later, on Sunday the 10th of May. And interestingly, the positivity rate was 0.24%, around 136,000 individuals in England which we thought was enormous. Miles Fletcher  Oh, well we’ll have a lot to say about what we've actually found. But just thinking about those early days and having to achieve in a matter of just a few days, what would normally take months. Tina Thomas, what was your reaction? What was your reaction when you first heard about this project and what it was trying to achieve? Tina Thomas, Deputy Director for the COVID-19 Infection Survey My reaction! So, before COVID, I was running the ONS social survey field community, and that's about 1,200 people, 1,200 interviewers, so they were keeping me busy. I had a phone call from one of our deputy directors on a Sunday night. They said, they want us to run an infection survey and they need me for the operations. And to be honest with you Miles, last year was a little bit of a blur. Usually, when we do surveys like that we take our time in working out the actual survey model, how are we going to do it, what we need, what our end goal is. And like Sarah has just articulated, everything was needed within days and weeks. To submitting a protocol on a Friday to recruiting our participants and the field staff out in the field, collecting the swabs and asking the questions was just short of 10 days, I believe, which was just something that we had never, ever done before. Did we think we could do it? There was a lot of nervousness but there was also so much passion to get this out there because we knew how important this data was. And everybody who worked on this, as Sarah said before, a huge collaborative effort to get it started. But it was just something that none of us had ever tried to tackle before. And it just proves what you can do. At pace, under pressure – we did it. Miles Fletcher And it's a huge collaborative effort involving not just Sarah and her academic colleagues at Oxford, but also the University of Manchester, a whole fleet of specialist contractors helping us to run the field study and specialist providers of all sorts right across the country. And, of course, government partners, chiefly the Department of Health and Social Care in England and the devolved administrations in Scotland, Wales and Northern Ireland. This is a huge UK-wide effort. Now in those early days, of course, it's the start of the survey, it started in a relatively small scale. It was, as I recall, about 12,000 households to start with, but then it grew rapidly didn't it? Tina Thomas Yes, that's right. I think it was, it was changing hourly some days. But yes, it started off relatively small and then it was within a matter of days “we want 150,000 unique participants providing swab samples across the UK”. We started off in England, we didn't actually bring any of the devolved nations onboard until around about the summertime, so a couple of months after the study had been running. That involved Scotland, Northern Ireland and Wales, which really brought its own operational challenges. Scotland and Wales are obviously a bit more rural than England. They wanted us in Scotland to go to the highlands and the islands and of course, going into Wales everything had to be translated into Welsh. And we had to make sure that we had Welsh speakers who could answer the phones for queries and also study workers that could speak Welsh as well. So really what was going on in the background from an operational perspective was very, very much like the swan analogy. We seemed quite calm on the surface, but with so much going on underneath - it was just incredible. And it's not just about recruiting those participants and getting the study workers out there. There's all the logistics around it, like how do we get the swabs to the labs? How do we get the test results back? Who's going to do all our printing? Who's going to send all the letters out? I'd wake up in the morning and think okay, so what challenge are we going to have to deal with today and I was never disappointed. Miles Fletcher And meanwhile always this huge expectation, from government, from the media, from ordinary citizens wanting to know exactly where the infections were, where the path of the virus was going. And during those very hectic early days, just one operational upset could throw the whole schedule into disarray. Fifteen months on, the survey is settled into a regular, pretty steady pattern now of hundreds of thousands of enrolled participants. And from their number, a large group taking a regular finger prick blood or swab test. How is that? Has it become easy to run now or are there still huge challenges out there? How are people, how about the participants themselves? How have they responded? And what's been their role in keeping this study running and keeping its findings meaningful? Tina Thomas So yeah, I mean, at this moment in time, we've got just over 457,000 live participants in CIS, 5.5 million swab tests have been taken to date. And just under a million blood tests. A daily rate for swab test is around 14,000, there's about four and about 5,000 blood tests being taken as well. We couldn't do this without our participants. Last year, when we had lockdowns, we had a bit of a captive audience. So, the study workers could get through their appointments. As we've seen lockdown restrictions lifted, it started to make operations a little bit more difficult. So, we've had to kind of pivot and change the way our study workers operate. So that's maybe working more in the evenings, offering weekend appointments. But our participants are just absolutely critical to this. And we can't thank them enough. It takes a lot of their time. We're asking a lot of them, but they majority of our participants are just really willing to do this. And you know, actually quite enjoying being in surveys while really feeling like they're making a difference. Miles Fletcher Tina, talk us through - we've got this small army of people out there in the field, covering households up and down the UK, tell us how the process works. Tina Thomas It's not such a small army, there's just over 3,000 study workers that are contracted to work on CIS, as you said, spread all across the UK. They are given what we call an allocation each day. So that's about visiting households to keep within protocol. So, some are still on weekly visits, some households are on monthly visits, they have to think ahead and have all their kit together: barcodes, test tubes, the swabs, the blood kits, and their mobile devices. So, they ring a household, usually the night before and agree a date and a time for them to visit. When they arrive at the household it’s a non-contact visit and they hand over the kits to the household members and scan the barcodes to make sure that we get the right test against the right person when they go to the labs. That's for swabs only. If the household is blood too then it's on to the fingerprick blood tests, which the participants usually take inside to do. And then they come back to the doorstep and there is a questionnaire that they'll need to answer, which Ruth touched on, which is about if they've had COVID, if they've had symptoms, what their social interaction has been like, and obviously that's more and more important now that lockdown restrictions are being lifted. Then the study worker completes the visit. And at some point during that evening they will drop the swabs off at a courier point where they'll go overnight to the labs. And the test results are usually back within two to three days. We've recently just introduced a new process, which saves quite a bit of money and also a lot of trees in that the test results now go out to our participants by email rather than by letter. If it's unfortunate to be positive, it gets notified to test and trace who then get in contact with the household. Miles Fletcher And of course, running something on this scale, it doesn't mean things always run entirely smoothly. We've had some quite colourful encounters on the doorsteps… Tina Thomas We have! So we have had a couple of study workers who've arrived at a pre-agreed date and time for the door to be opened by somebody who wasn't wearing any clothes. That's happened a couple of times and I think actually one study worker did ask the gentleman to go and put some clothes on and he came back with a T-shirt on, which just about covered his top half. And with the finger prick blood test as well, so it's quite a neat kit that comes in a cardboard box and it's got a plaster and a lancet and the test tube that we need them to collect the blood. The lancets are not needles, they're tiny, tiny blades because the actual volume of blood that we need to test is quite high. But we have had a couple of participants who I think were laborers on building sites, whose hands were very calloused from the job that they do, where the lancet just would not pierce the skin. And because they were so willing to provide that blood sample and wanted to provide that blood sample, I think we've had a couple of instances where they've come back with Stanley knives and actually managed to get blood out the finger with that. We wouldn't approve that or suggest that's the best way to do it. But what it does show, certainly the last one, is that people are just so keen and passionate to be included in this survey that they'll do what they can to help us. Miles Fletcher Made of sterner stuff than me, willing to take a stanley knife to yourself in the cause of science. And please, everybody don't try that yourselves. Some people haven't been quite so robust on the doorstep though. Tina Thomas No. Since we introduced the fingerprint blood test for antibodies, we have had a number of participants who have fainted whilst trying to get a blood sample for us. And unfortunately, a very high percentage of those are men. But we do have procedures in place with a study worker to help people when that happens. And obviously it remains a non-contact visit. But they have got a list of instructions if somebody does, unfortunately, pass out. And I think at this point as well, Miles, I'd really like to just say a massive, massive thank you to our study workers working on this who have been out doing this, during those early dark days of the pandemic, through every type of weather you can think of, to get us these samples and the data that we need. Miles Fletcher Thank you, Tina. So Ruth, this is where you come in – the field force have gone out, they've done their job, they've gathered in these thousands and thousands of samples, what do you do first? Ruth Studley, Head of Analysis for the COVID-19 Infection Survey So, what happens first is all of those swabs are sent to the different Lighthouse Laboratories to be tested using different PCR arrangements. That is part of the national testing programme and we use exactly the same process as the rest of the UK, that then gives us a set of data which we could use. And that is sent to us securely in ONS, where we process that data to understand exactly what is going on in the raw data before we use our modelling arrangements to produce our headline estimate. So, as part of looking at that data, we want to know things like what the different cycle threshold value is, for example. Now that is a bit of a technical term, and if I try and describe it very basically, it's the number of times, the number of cycles that each PCR test has to go through before a positive result is detectable, for example. And if there's a high quantity of the virus, you would expect that to be identified after a low number of cycles. So we would say that that was a low CT test, and it will be regarded as a high viral load. And so we look at things like that. And there's lots and lots of different things that we would look at in the raw data before then moving on to doing our modelling. The modelling that we use is a Bayesian multilevel regression post stratification model. And that's used to calculate breakdowns of positivity by region, and age across England. That all happens at breakneck speed. So the data arrives on day one, and we are virtually ready to produce information by day three, we publish by day five. It's very, very rapid. I'm not sure if any other official statistics are produced that rapidly. Miles Fletcher But such as the need for that data. Have the findings ever surprised you? Ruth Studley Yes and no. So, you wouldn't expect it to change very rapidly in the course of a few days. And usually, if there is something that you were surprised by, it would usually be an indicator that you want to do some further analysis. And there have been occasions where we've seen things and thought, does that make sense? And you dig a bit deeper, and you find that there's something going on in the data. But whilst, like Sarah was saying, you would never propose to predict what is going to happen, you would expect the changes to be relatively smooth. Miles Fletcher So, out on the doorstep every day, 12,000 swab and blood tests being taken, on average, at the moment nearly 6 million in all gathered under this survey. But what happens to those test results when they come in? Ruth, it's your job to make sense of them, and to turn them into statistics that can be relied upon. What's the secret to keeping those estimates reliable and trusted? Ruth Studley So that's a really great question Miles. I was thinking when I was listening to Sarah and to Tina then, what is it about this team that has allowed us to produce such fantastic results that have been so vitally important to the UK? And I think it’s the three Ps you know, we've got people who are passionate, people who work at pace, and we work in partnership. And it's all about wanting to do the right thing for the country, actually. So, what do we do with all of that data? We have a plethora of information as you have all described. And we do collect information from every participant every time we visit them on their socio demographic characteristics: whether they are experiencing symptoms, whether they are self- isolating, what their occupations are, whether they're working at home, questions about long COVID and whether they've been vaccinated, social distancing, physical distancing, etc. We ask all sorts of different questions, because it's really important that we're able to provide as much information as we can, not only about the direction of the pandemic, but also what people's experiences are in the community. And it's probably worth just reflecting there about who it is that we are sampling and who we're representing. This is a survey of the community of the population at large. So we will be testing people who are both symptomatic, but also are not experiencing symptoms. And that's really important because we know that our data has shown us that over the last 12 plus months, that people very often have tested positive but not had symptoms. And so this is a real reflection of what people will experience at large. And every week, we use a number of modelling techniques to estimate the number of people who are testing positive for the virus. And we produce that every week. You will see it in the media and on our website every Friday lunchtime, where we provide estimates of the number of people that are testing positive for infection. But as I mentioned, we asked lots of questions. So we break that down by lots of different characteristics, so by age by region, we do it for the four countries in the UK, and so on. And we do that very much in partnership with our academic partners of which Sarah is a really, really key partner for us. Miles Fletcher So that every week when you produce the estimates, we can say not just what's going on in Scotland or England at that level, but how local can you make the data to make people aware of what's happening in, you know around the corner? Ruth Studley We're really mindful that people are interested in what's happening locally to them. So we've also been able, because we have quite a large sample, to do quite sub-regional estimates. And that has provided a granularity of information for both decision makers, but also for the general public who are interested in what's happening in their locality. The geographies that we're able to get into the detail of are, within England, about 100 sub regions to give you a feel for the size of it. Miles Fletcher Now, tell us then about the ongoing story the data have been telling us after the first wave. After that, not surprisingly, we found quite a low level of prevalence in those early readings. But what was the story from then on, what happened after that? And what have been the key moments from an analyst’s point of view do you think in the path of this pandemic? Ruth Studley That's an interesting question. Over the course of the autumn last year, we did start to see a general steady rise, or just before Christmas with the identification of the Alpha variants as we now know it. And an awful lot of work went into that because as part of the swabs that we take and the analysis we do, we are able to do additional analyses to try to identify different variants and that is absolutely critical. There were some key points there obviously, because our information was part of the suite of information that government uses to help make their decisions around all the different interventions that they wanted to put in place, such as the different lockdowns across the UK. So the infection rate was steadily rising, and it peaked in January 2021. All of the days over the last 18 months have very much gone into one, but it peaked in January 2021. And then we started to see a steady decrease over the next couple of weeks and months with various different interventions occurring and then obviously we saw the arrival of Delta variant, and that has had an impact. And within certainly months, if not weeks of identification of that it became the dominant variant across the UK. And we are now seeing that the data has increased. Miles Fletcher And as you say, it's the Delta virus that really changed things suddenly midway, if you like, through the pandemic. Sarah, would you say that that's been the most important finding of the study so far? Professor Sarah Walker Well, I mean, I think it's easy to focus on Delta. But you know, frankly, Alpha was pretty terrible in December. I think it's actually been incredible to think that, frankly, in the space of only six months, the virus went through two such massive changes, which basically doubled transmissibility every time. So Alpha was twice as transmissible and Delta was twice as transmissible  again. Of course, what is different is that we now have vaccinations and I think that is somewhere where the survey is increasingly really making a major contribution, because linked data is really brilliant and we can do a lot of stuff with it. But we're not really able to adjust very well with the kind of large scale NHS linked data, for characteristics that do affect people's chance of testing positive, whereas in the survey, because as researchers we collect this detailed information every month, we're able to adjust for things like whether people are healthcare workers, when they work in care homes, smoking status. Things that actually do make a difference to your risk of testing positive: whether they have been to a hospital. And so we're able to get much better estimates of the impact of vaccines on infection rates, really in the community, than many of these other big studies. Of course, we can't do it all, we can't look at hospitalizations, because they're quite rare in our study, but we can actually make a really big contribution. Miles Fletcher And that's all because the study worker as well as taking the taking the test sample sits down and actually goes through the questions with gets a lot more information from them. Sarah Walker Absolutely.  And then also at the antibody testing, which we're now doing on around a half of our participants who are giving us finger prick blood every month, and that's  enormously valuable in tracking levels of antibody protection in the community as a whole and then trying to understand how that relates to infection rates in different age groups and different parts of society. Miles Fletcher And that's the particular value of testing the same group of people again, and again. Sarah Walker And actually also because it turns out that one of the really fascinating findings is that people who've had COVID before, if they get vaccinated they do even better. But in order to find that out, you need to know who's been infected before. And because we've been testing our participants every month, some people now for nearly 18 months, we have a really good history. We won't catch every single infection but for most people we have a really good idea about who's had COVID or not. And again, that allows us to make much better estimates of the impact of vaccination, the impact of natural infection, and then how the two work together. Miles Fletcher   And that's because the survey has covered the period right before the introduction of the of the vaccines right through their mass rollout. And according to the data you produce, towards the end of the summer, we're starting to actually see some of that vaccine induced positivity actually reducing once again, and new questions arise about booster jobs and so forth. What remains to be learned about the effect of those vaccines and about the longer-term impacts of COVID more generally? Sarah Walker There's a really huge emphasis on boosters at the moment, Miles, and I understand from the point of view of individual people, particularly if they are having their antibodies tested, and they see it go positive to negative, they may feel some concern, but it's really important to understand that the immune system has got memory. And actually you can have low levels of antibodies, but actually, the immune system remembers, and if you get exposed to COVID again, you get a burst of activity, and you are actually protected, particularly from hospitalization and death. And ultimately we've got to find a way to live with this virus, we aren't going to eliminate it and we can't keep vaccinating 50 million people a year. And so what we're trying to do as we move forward is to stop people ending up in hospital and stop them dying, whilst understanding that the virus is going to be with us. And I think the survey has really got a crucial role in answering some of the questions around what kind of levels of background infection can we live with. Are there thresholds of background infection, which then do trigger increases in hospitalizations, which obviously we can't live with? You know, who actually needs boosting in order to stop them ending up in hospital, as well as who maybe needs boosting in order to stop them getting infection, but infection that particularly leads to bad consequences. Obviously, antibodies are only part of the picture, we also have T cells and other things that help protect us from infection. I think over the next six months, the survey will really help us unpick some of those answers and really, it's about helping us learn how to live with this, because we aren't going to get rid of it. It's still a brand new virus. I mean, 18 months ago, we didn't know it existed. The beginning of March 2020, there was stuff in the papers about this virus in this Chinese city, but no one had any idea. And no, we still have a huge amount to learn. And the survey can really, really help.   Miles Fletcher Vital then, that it keeps going. It’s one thing I’ve discovered in working on the media side of ONS, and like everything at ONS we try and show with numbers, it’s interesting how media attention for our estimates goes up and down according to the level of infection. Is there a danger more broadly do you think then that people might think at this stage that we’re seeing deaths and hospitalisations thankfully at fractional levels of what they were before, but people might still think that it’s all over really, that we don’t need to take this as seriously as we did, and Ruth how do we get the message out about the importance, the continuing importance of trusting the data?   Ruth Studley So Miles I think one of the key things, you talked about the benefits of the longitudinal aspects of the survey, going back to the same people week in, week out. One of the critical benefits of this survey has been our ability to respond and be relevant to what decision-makers need. Sarah’s done some fantastic work and I’ll let her talk about the work that she’s done around vaccine effectiveness, but actually being able to understand and pre-empt and work with our users to understand what is critically needed is one of the real benefits of this survey. Because not only do you have that breadth of data and that wealth of data, but being able then to link it across ONS to some of our other data sources, whether that is the immunisation data or other data sources that we might hold within ONS, all adds a huge amount of value. Miles Fletcher Sarah, just looking at that international dimension again, are other countries running studies like this? Sarah Walker So, to my knowledge there isn’t another study like this in the world, both in terms of its length and the fact that it has been going since April 2020, but also in particular its size and representativeness of the general population. Generally what other studies are doing is relying on testing data, so relying on linking information about people who come forward to be tested in national testing programmes, either because they have symptoms or other reasons like workplaces. And of course, whilst that data is very powerful and is very large, not everyone who has symptoms takes a test and certainly there are plenty of people who have Covid without symptoms who never know they need a test. So, you know there are some real limitations of using that data, so from that point of view the survey really has got huge benefit and that benefit is recognised by policy bodies including the WHO in terms of particularly informing questions around vaccine effectiveness where being able to do the kind of adjustments that we do is really so important. Miles Fletcher So the survey has established itself as well, what the Times no less calls the most reliable measure of infection rates provided by the UK government. That speaks loudly because the media in the UK don’t hand out compliments for nothing: that’s a powerful testimony to how this study has established itself and it remains central to the UK’s research effort, and we’re told is to some degree unique in the world. Thank you to all three of our guests Tina Thomas, Head of Survey Operations, Ruth Studley Head of Analysis and from Oxford Professor Sarah Walker. Next time we hear the inside story of the 2021 Census and hear about the challenge of getting responses from every household in England and Wales during a period of national lockdown. You can subscribe to new episodes of this podcast on Spotify, Apple Podcasts and all the other major podcast platforms. You can also get more information by following the @ONSfocus Twitter feed. The producers of Statistically Speaking are Elliot Cassley and Julia Short, I’m Miles Fletcher, goodbye.

Statistically Speaking is the Office for National Statistics' regular monthly podcast, offering in-depth interviews on the latest hot topics in the world of data, taking a peek behind the scenes of the UK’s largest independent producer of official statistics and exploring the stories behind the numbers.