Superforecasting: The Art and Science of Prediction

by Philip E. Tetlock

No one had ever seriously tested the forecasting accuracy of political experts and the more I pondered the challenge, the more I realized why. Take the problem of timelines. Obviously, a forecast without a time frame is absurd. And yet, forecasters routinely make them, as they did in that letter to Ben Bernanke. They’re not being dishonest, at least not usually. Rather, they’re relying on a shared implicit understanding, however rough, of the timeline they have in mind. That’s why forecasts without timelines don’t appear absurd when they are made. But as time passes, memories fade, and tacit time frames that once seemed obvious to all become less so. The result is often a tedious dispute about the “real” meaning of the forecast. Was the event expected this year or next? This decade or next? With no time frame, there is no way to resolve these arguments to everyone’s satisfaction—especially when reputations are on the line.