Eliezer Yudkowsky of Overcoming Bias fame has written a fabulous blog post showing why people consistently underestimate time requirements for their projects. This is also know as the “planning fallacy”. The fallacy occurs even when you ask people to adjust for it:
A clue to the underlying problem was uncovered by researchers who found that asking subjects for their predictions based on realistic “best guess” scenarios, versus asking subjects for their hoped-for “best case” scenarios, produced indistinguishable results.
Nor can it be adjusted for by asking for specific plans – in fact the more specific the plan the more people overestimate how much they can accomplish. Fortunately, there is something very simple you can do:
A group of Japanese students expected to finish their essays, on average, 10 days before the deadline. They actually finished 1 day before deadline. Asked when they’d finished previous essays, they said: “One day before deadline.”
So, the next time someone you are working with shows you a project plan (or worse still, a detailed project plan) ask them:
- how long did it take you to complete these tasks last time?
- what has changed between the last time and this time that makes you things will go more quickly?