Abstract
Market e¦ciency survives the challenge from the literature on long-term return
anomalies. Consistent with the market e¦ciency hypothesis that the anomalies are
chance results, apparent overreaction to information is about as common as underreaction,
and post-event continuation of pre-event abnormal returns is about as frequent as
post-event reversal. Most important, consistent with the market e¦ciency prediction that
apparent anomalies can be due to methodology, most long-term return anomalies tend to
disappear with reasonable changes in technique. ( 1998 Elsevier Science S.A. All rights
reserved.