Is Information Uncertainty Positively or Negatively Associated with Post-Earnings-Announcement Drift?

This study reconciles conflicting evidence from prior research about the association between information uncertainty and post-earnings-announcement drift (PEAD). According to traditional PEAD studies there should be a positive association between PEAD and uncertainty about the implication of an earnings announcement for future earnings, referred to in this paper as "information uncertainty. Empirical studies have documented both positive and negative associations, however. In particular, studies that use analyst forecast dispersion as a proxy for information uncertainty report a negative association between information uncertainty and PEAD. Although the authors of those studies argue that their results are consistent with behavioral finance theories, a negative association between information uncertainty and PEAD is troubling because it is not consistent with the notion that more reliable information improves market efficiency. In fact, previous empirical studies that use proxies for information uncertainty other than analyst forecast dispersion find a positive association between information uncertainty and PEAD. This paper argues that the negative association between analyst forecast dispersion and PEAD can be explained by "herding behavior immediately after earnings announcements. I introduce an analyst-based proxy for information uncertainty that controls or mitigates the effects of herding on forecast dispersion. I find that, after controlling for the effect of herding, there is a positive association between information uncertainty and PEAD even when analyst forecasts are used to measure information uncertainty.