Mutual funds typically invest a disproportionately large portion of their portfolio in one industry (main industry). We present a simple theoretical model to demonstrate that better mutual fund managers make larger investments in the important supplier/customer industries related to the main industry. Consistent with our theory, empirical tests on a large sample of mutual funds show that investment in related industries is positively associated with fund performance and plays a more significant role in explaining fund performance than investment in the main industry. Furthermore, the positive relation between main investment and fund performance obtains only when related investment is high.

There is a tenuous link between market efficiency and economic efficiency in that stock prices are more informative when the information has less social value. We investigate this link in the context of CEO turnover. Our theoretical model predicts that, when the board’s monitoring intensity and the informed trader’s information decision are jointly endogenized, stock price informativeness is negatively related to the board’s monitoring effort. Our empirical tests provide supporting evidence for this negative effect. Moreover, using the passage of the Sarbanes–Oxley Act (SOX) as a quasi-natural experiment, we find that SOX, while strengthening corporate governance, has a negative effect on stock price informativeness, especially among firms with complex organizational structures.