Planning fallacy: what it is and what it means

The planning fallacy is the systematic tendency to underestimate completion times, documented by Buehler, Griffin and Ross. Research shows that this bias is systematic and resists even direct experience: even someone who has done a task dozens of times tends to plan with excessive optimism. The phenomenon shows up in daily planning when blocks regularly overrun and swamp the blocks that follow. The operational fix is to track the actual time of recurring activities, replacing intuitive estimates with empirical data.

Distinctive: resists even direct experience
Distinctive: systematic and resists
Essential: systematic tendency to underestimate
Essential: completion times
Essential: plan with excessive optimism
Constant: even someone who has done a task dozens of times

Glossary

Planning fallacy

A systematic tendency to underestimate the time needed to complete an activity, which persists even in people who have done the task many times.