We haven’t seen a lot of great comedic writing about the ongoing credit crisis. Megan McCardle, however, reminds us that economics is, ultimately, a branch of psychology. She then unpacks the various psychological tendencies that piled up the kindling for the financial markets. One of them is "optimistic bias," which she defines: "People tend to be overconfident about their own abilities and the outcome of their plans. Something like 90% of people think that they are above average drivers less likely to get into an accident than the average joe. This is so pervasive that there is actually a scientific name for the few people who accurately assess their own future, their abilities, and what other people think of them: clinically depressed."