In this paper, we study whether the creation of a uniform Nordic and Baltic stock trading platform has affected weak-form information efficiency. A time-varying measure of return predictability for individual stocks is used in a panel-data seting to test for stock market merger effects. The results indicate that the stock market consolidations have had a positive effect on the information efficiency and turnover for an average firm. The merger effects are, however, asymmetrically distributed, indicating, among other, a flight to liquidity effect, i.e. relatively large (small) firms located on relatively large (small) markets experience an improved (reduced) information efficiency.