S&P 500 index mutual funds

The commodity-like nature of index mutual fund portfolios suggests that price competition should be more evident than with actively managed funds. After all, fund managers operate index funds not to beat their benchmarks or actively managed funds, but to mimic benchmark portfolios and performance, less expenses. Therefore, fund expenses should be singularly important in explaining and predicting differences in index fund performance. Haslem (2003) addresses the broader issues of fund expenses.