Discussion of “Post-Earnings Announcement Drift and Market Participants' Information Processing Biases”

Liang (2003, this issue) hypothesizes that the predictable stock price drifts that occur after earnings earning announcements increase with (a) divergence in analyst beliefs and (b) the reliability of publicly reported quarterly earnings. Whereas the prior literature has generally hypothesized that drifts are caused by the inability of the stock market to fully appreciate predictable autocorrelation in seasonally-differenced quarterly earnings, this paper relies on cognitive biases proposed in the behavioral finance literature. While the results are consistent with these predictions, my discussion raises possible reasons why it may be premature to conclude that the cognitive biases discussed here cause drifts.