Irrational Mutual Fund Managers: Explaining Differences in Their Behavior

Documenting the disposition effect for a large sample of mutual fund managers in the United States, we find that stock-level characteristics explain the cross-sectional variation of the effect. The disposition effect, which is the tendency to sell winner stocks too early and hold on to loser stocks for too long, is more pronounced for fund managers who invest in stocks that are more difficult to value. Using different measures of stock and market uncertainty, we show that mutual fund managers display a stronger disposition-driven behavior when stocks are more difficult to value. We also find that the level of the disposition effect is monotonically increasing with the level of systematic risk (i.e., beta). In addition, we document that the trading behavior of mutual fund managers is partly driven by attention-grabbing stocks (dividend-paying stocks). Overall, our results suggest that stock-level uncertainty and trading of attention-grabbing stocks amplify the disposition effect and that differences in the effect can be explained by mutual fund managers' investment styles. Given that mutual funds hold a large fraction of the U.S. equity market, our findings add to the ongoing discussion whether professional investors can create stock mispricings and shed new light on market efficiency.