In a recent article, Black [1] introduces a type of trading that he terms noise trading. He asserts that noise trading, which he defines as trading on noise as if it were information, must be a significant factor in securities markets. However, he does not provide an explanation of why any investors would rationally want to engage in noise trading. The goal of this paper is to provide such an explanation for one type of investor, managers of investment funds. As shown here, the incentive for a manager to engage in noise trading arises because of the positive signal that the level of the manager's trading provides about his or her ability to collect private information concerning current and potential investments. If the manager's compensation is directly related to investors' perceptions of his or her ability, the manager will then trade more frequently than is justified on the basis of his or her private information. In addition to providing this explanation for noise trading, the results of this analysis may also be useful for further empirical exploration of the relation between investment fund portfolio turnover and subsequent performance.

We document that stocks with the strongest prior 12-month returns experience a significant average market-adjusted return of 1.58% during the five trading days before their earnings announcements and a significant average market-adjusted return of −1.86% in the five trading days afterward. These returns remain significant even after accounting for transactions costs. We empirically test a limited attention explanation for these anomalous returns—that stocks with sharp run-ups tend to attract individual investors’ attention and investment dollars, particularly before their earnings announcements. Our analysis suggests that the trading decisions of individual investors are at least partly responsible for the return pattern that we observe.

This paper presents evidence of anomalies in internet firms’ stock returns surrounding their quarterly earnings announcements. There is a general runup in prices in the days prior to the earnings announcements, followed by a price reversal lasting for several days. The magnitude of the market-adjusted returns associated with these price movements exceeds 11 percent over a 10-day period. We find little evidence to suggest that these returns can be explained either by the earnings news disclosed or by risk changes. Additional analyses suggest that these return patterns are driven, at least in part, by price pressure.