Price effects of horizontal mergers: a retrospective on retrospectives

In this comprehensive review of ex-post merger studies price effects of horizontal transactions are evaluated. By combining and further analyzing the results of 52 retrospective studies on 82 mergers or merger-like transactions it can be shown that the industry alone is no strong indication for the direction of price-related merger effects. However, the “size” or “importance” of a transaction as well as market concentration pre-merger and change in concentration due to the transaction seem to have an impact on post-transaction price development