How do different types of investors react to new earnings information?

The purpose of this study is to investigate how different types of investors react to new earnings information. Using the extremely comprehensive official register of share holdings in Finland, we find that the majority of investors are more likely to sell (buy) stocks in a company after a positive (negative) earnings surprise and that they are biased towards buying after the disclosure of an annual report. Large investors show behaviour opposite to that of the majority of investors. We consider several possible explanations for this heterogeneous investor behaviour, of which differences in investor overconfidence emerges as the strongest candidate.