Understanding the Planning Fallacy: How we Underestimate Time to Complete Projects

The planning fallacy is a tendency to underestimate the time it will take to complete a project despite prior knowledge that similar projects have taken longer. Diagnosing and treating the planning fallacy can improve future planning endeavors. Roger Bueller and colleagues measured the planning fallacy using honors students working on thesis projects. The average prediction for thesis completion time was 33.9 days.