Drift or Jump: What Drives Post-Earnings Announcement Stock Returns?

Abstract

One of the contentious issues regarding the post-earnings announcement drift (PEAD) is whether the abnormal stock return is driven by investors’ delayed reaction to earnings information or by unexpected information shocks subsequent to earnings announcement. In this paper, we disentangle unexpected large changes in stock prices, known as jumps, from total stock returns. Although on average jump occurs only once per firm quarter, it accounts for up to 40% of the return differential between top and bottom SUE deciles. This is evidence that a significant part of PAED is driven by unexpected information shocks. Nevertheless, the drift component still explains at least 50% of the variation of anomalous PEAD returns. The findings suggest that PEAD cannot be entirely attributed to investors’ delayed reaction to earnings information, but neither can the hypothesis be ruled out. In particular, we find that delayed reaction is more pronounced following positive earnings surprises.