Investor Overconfidence and Trading Behaviors

How overconfident are individual investors, and how does overconfidence affect their investing practices? In his November 2011 paper entitled “Financial Overconfidence Over Time | Foresight, Hindsight, and Insight of Investors”, Christoph Merkle examines relationships between the return/risk expectations of affluent, self-directed private investors and their trading activity, diversification and risk taking. To frame the relationships, he considers three elements of overconfidence:

1. Overplacement: “I am better informed, more experienced and more skillful in investing than average.”
2. Overprecision: Confidence intervals for expectations are too narrow (expected volatility is too low).
3. Overestimation: Recollected performance is higher than actual performance.

Using quarterly survey data (617 total respondents, with at least 130 in each of nine rounds) and associated investment portfolio characteristics/activity (49,372 trades) for several hundred investors having online brokerage accounts with a UK bank between June 2008 and December 2010, he finds that: (more…)