In his 1998 paper "A Portrait of the Individual Investor," Werner De Bondt conducted fascinating research on individual investors by monitoring behavior of people in investment clubs. He recruited 45 investors (30 men, 15 women) from the National Association of Investment Clubs for his study. For 20 weeks, De Bondt tracked the group's forecasts for the future performance of the Dow Jones Industrial Average and of their own equity holdings. The study produced four key findings:
- Investors were more optimistic about the future performance of their equity holdings than they were about the performance of the Dow. As a matter of fact, the predictions about the return of their holdings were three times that of the Dow.
- They underestimated the volatility of their equity holdings.
- Their forecast of their own portfolio was anchored on past performance.
- They underestimated the degree to which their stocks moved with the overall market.
De Bondt's study showed that investors tend to be overconfident and tend to discount the benefits of diversification. This is a dangerous combination. Next, we'll learn how our behaviors can make us overconfident.
Follow the series: Our Own Worst Investing Enemy
- Why Overconfidence Is a Problem
- Putting Our Investments in One Basket
- How We Make Retirement More Difficult
- Forecasting Should Be Left to the Astrologers