We study standard mutual fund performance measures, using simulated funds whose characteristics mimic actual funds. We find that performance measures used in previous mutual fund research have little ability to detect economically large magnitudes (e.g., three percent per year) of abnormal fund performance, particularly if a fund's style characteristics differ from those of the value‐weighted market portfolio. Power can be substantially improved, however, using event‐study procedures that analyze a fund's stock trades. These procedures are feasible using time‐series data sets on mutual fund portfolio holdings.

Economic distortions can arise when financial claims trade at prices set by an intermediary rather than direct negotiation between principals. We demonstrate the problem in a specific context, the exchange of open‐end mutual fund shares. Mutual funds typically set fund share price (NAV) using an algorithm that fails to account for nonsynchronous trading in the fund's underlying securities. This results in predictable changes in NAV, which lead to exploitable trading opportunities. A modification to the pricing algorithm that corrects for nonsynchronous trading eliminates much of the predictability. However, there are many other potential sources of distortion when intermediaries set prices.

Existing studies of mutual fund market timing analyze monthly returns and find little evidence of timing ability. We show that daily tests are more powerful and that mutual funds exhibit significant timing ability more often in daily tests than in monthly tests. We construct a set of synthetic fund returns in order to control for spurious results. The daily timing coefficients of the majority of funds are significantly different from their synthetic counterparts. These results suggest that mutual funds may possess more timing ability than previously documented.