Scott mentioned that fact about superforecasters in his review; from what I remember the book doesn’t add much detail beyond Scott’s summary.
One result is that while poor forecasters tend to give their answers in broad strokes – maybe a 75% chance, or 90%, or so on – superforecasters are more fine-grained. They may say something like “82% chance” – and it’s not just pretentious, Tetlock found that when you rounded them off to the nearest 5 (or 10, or whatever) their accuracy actually decreased significantly. That 2% is actually doing good work.
Scott mentioned that fact about superforecasters in his review; from what I remember the book doesn’t add much detail beyond Scott’s summary.