According to theory, trading volume decreases in information asymmetries, i.e. when there are differences in information. This is due to the fact that uninformed investors delay their trades when they are facing adverse selection. When the asymmetry is resolved there should be a corresponding increase in trading volume. Around earnings announcements (scheduled an-nouncements) this asymmetry is greater than normal, hence one can expect a decrease in trading volume. Around unexpected announcements such as acquisition announcement (unscheduled announcements) a total increase is instead expected because of an increase in trading by informed investors. All these effects are likely to be greater for smaller stocks.

The purpose of this thesis is to investigate the trading volume before- and after scheduled announcements and the trading volume before unscheduled announcements in order to investigate how informed- and uninformed investors behave in information asymmetries on Stockholmsbörsen.

The method is quantitative with secondary data from the Stockholm Stock exchange from 1998-2004. The method is the same as Chae (2005) uses with paired-samples t-tests. It tests whether the change in trading volume is different from a benchmark consisting of an average of the trading volume 30 days before the announcement.

We found a statistically significant decrease in trading volume in 6 of 10 days before a scheduled announcement and an increase also on 7 of 10 days after the announcement. For unscheduled announcements we found an increase before it was released but were not able to prove it statistically. We conclude that uninformed investors behave strategically before scheduled announcements in order to avoid adverse selection. We could not conclude that the effects are greater for smaller stocks.