Is There a Good Metric for Learning in an Incremental Reading System?

A number of items and like the status bar, those are examples of core sort of metrics for learning in like an incremental reading system. Do you think it's possible to design like a good metric? Because it seems to me like a really good metric of learning has to involve things that take place outside of the system. For example, being able to read a book, I suppose, or converse with a native speaker,. Those are the progress metrics that you really want to achieve.