Forecasting Error - Is Your Opinion Right?

In deciding which future to prepare for, you need two things: an opinion about what's likely to happen and a view on the probability that your opinion is right. But one of our favorite sayings around oak trees states that it's one thing to have an opinion, and something very different to act as if it's right. Clearly, our opinions are our opinions because we believe them. We rarely hear anyone say, here's what i think, and i'm probably wrong. Yet as i see it, most people who believe in forecasting come up with their opinions and then act on them with equal amounts of confidence. This is one of the greatest sources of investment error.