Are Investors Rational? Choices among Index Funds
研究发现标普500指数基金收益差异超2%，投资者选择与业绩关系弱于理性预期，低成本或高历史回报策略优于投资者实际选择。
ABSTRACT S&P 500 index funds represent one of the simplest vehicles for examining rational behavior. They hold virtually the same securities, yet their returns differ by more than 2 percent per year. Although the relative returns of alternative S&P 500 funds are easily predictable, the relationship between cash flows and performance is weaker than rational behavior would lead us to expect. We show that selecting funds based on low expenses or high past returns outperforms the portfolio of index funds selected by investors. Our results exemplify the fact that, in a market where arbitrage is not possible, dominated products can prosper.