This from David Brooks of The New York Times.
"Humans are overconfident creatures. Ninety-four percent of college professors believe they are above average teachers, and 90 percent of drivers believe they are above average behind the wheel. Researchers Paul J.H. Schoemaker and J. Edward Russo gave computer executives quizzes on their industry. Afterward, the executives estimated that they had gotten 5 percent of the answers wrong. In fact, they had gotten 80 percent of the answers wrong."