Agreeing to disagree: Informativeness of sentiments in internet message boards

Abstract

We study the informativeness of the sentiment of posts on Australia's largest online stock message board, HotCopper. We explore whether disagreements among sentiment form a signal about the fundamental news of a company. We find that positive sentiment is associated with noise induced (uniformed) trading whereas negative sentiment contains value-relevant information about a firm's performance. Our empirical findings suggest that short selling activity reduces overreactions of abnormal returns in a noisy environment on the same day. Furthermore, we observe a sentiment convergence pattern around annual earnings announcements and low levels of sentiment homogeneity relate to significantly lower annual earnings surprise. This supports the view that disagreements among sentiments are a signal of bad news about firm fundamentals.