The Planning Fallacy: Symptoms and Examples

Researchers, including Roger Bueller, measured the planning fallacy by asking students to predict when they'd finish their theses. The average prediction was 33.9 days, but it actually took 55.5 days - a 64% overage. The planning fallacy was also found in stock brokers, electrical engineers, doctors, and everyday activities like Christmas shopping or waiting in line. So what's wrong with us? Why is there such a gap between intention and behavior?