Investors with an “overconfidence” bias often trade too much and manage their portfolio on a stock-by-stock basis—while assuming they can beat the market, which the University of Chicago’s Mr. Thaler says probably won’t happen.
Mr. Thaler recommends a little test for the presence of an overconfidence bias. “Write down 10 traits [such as ‘investment skill’ or ‘ability to make good stock picks’], then ask yourself how you rate compared to your co-workers. If you rate yourself above average on all of them, plead guilty,” he says.
From the Wall Street Journal