"For example, we tend to judge the probability of something happening based on how easy it is to bring examples of that thing to mind. It's why people tend to buy earthquake insurance after an earthquake, although in reality that's when the risk is the lowest. It's why those of us who have been the victims of a crime tend to fear crime more than those who haven't. And it's why we fear a repeat of 9/11 more than we fear other types of terrorism."