The expert who knew the odds and used them on everyone but himself
A psychologist assembling a curriculum-writing team asked a colleague a simple question about timing — and got an answer nobody in the room wanted to believe applied to them.
In 1976, Daniel Kahneman was about a year into a project building a judgment-and-decision-making curriculum for Israeli high schools. The team, feeling good about their progress, wrote down private estimates for how much longer it would take to finish a draft. The guesses clustered around two years.
Kahneman then asked Seymour Fox, the curriculum expert on the team, to think of other groups that had built a course from scratch, starting from roughly the same stage they were at. How long had those projects taken? Fox went quiet, then answered: about 40% of comparable teams had eventually given up entirely. Of those that finished, none had taken less than seven years, and none more than ten. Asked whether their team had any advantage over those others, Fox said no — if anything, they were slightly below average in resources.
Everyone in the room, Kahneman included, had genuine expertise in exactly this kind of forecasting error. Nobody suggested scrapping the project. They quietly stopped discussing the timeline and kept going. The book was finished eight years later, matching Fox's number almost exactly, and the ministry that commissioned it had lost interest by the time it arrived.
Kahneman later named the error the planning fallacy — and the sharper lesson wasn't that we can't calculate the odds. It's that knowing the odds and applying them to your own plan are two entirely different acts, and the second one is the one that fails.