Why Does the Post Earnings Announcement Drift Last for So Long? An Explanation Based on the Investors' Beliefs

We examine the role of investors' beliefs in determining the post earnings announcement drift (PEAD). Specifically, we propose a technique to estimate the belief parameters of the informed and uninformed investors, based on which we define the uninformed investors' information acceptance ratio (IAR). We demonstrate that IAR is a key factor determining the length of PEAD. IAR also explains the post announcement returns and the risk increases. Furthermore, we show that the earnings announcements contain both the hard and soft information. The hard information reduces uncertainty, whereas the soft information enhances uncertainty. And the latter effect dominates the former