The planning fallacy is a tendency to underestimate the time it will take to complete a project while knowing that similar projects have typically taken longer in the past. Roger Bueller and some colleagues set out to measure the planning fallacy. Their first experiment used honors students who were working on their thesis projects. The researchers asked each student to predict when they'd submit their thesis. It actually took 55.5 days that's a 64% overage. Similar evidence of the planning fallacy among stock brokers and electrical engineers and doctors. They also found it in everyday activities like Christmas shopping, doing taxes, even waiting in line for gas. What's wrong with us? Why is there such a gap between intention and behavior