In the aftermath of 9/11, it is estimated that 1.4 million Americans chose to drive instead of fly, because they assessed the risk of getting on a plane to have multiplied many times. As a result, about 1000 extra people died on the roads.

It is precisely this human tendency to miscalculate risk, focusing on the spectacular but extremely unlikely event while ignoring the everyday causes of harm with infinitely higher probability, which provides the calculus of terrorism.