How Important are Earnings Announcements as an Information Source?

In a competitive information market, a single information source can only dominate other sources individually, not collectively. We explore whether earnings announcements constitute such a dominant source using Ball and Shivakumar's (2008) R2 metric: the proportion of the variation in annual returns explained by the four quarterly earnings announcement returns. We find that the earnings announcement days' R2 is 11 percent — higher than the corresponding R2 of days with dividend announcements, management forecasts, preannouncements, 10-K and 10-Q filings, and their amendments, and comparable to that of the four days with largest realized absolute return in a year. Additional analysis reveals that earnings announcements convey extreme bad news as often as management forecasts and preannouncements; for any other type of news earnings announcements are much more frequent. We conclude that earnings announcements are an important source of new information in the equity market