Using rival effects to identify synergies and improve merger typologies

Differentiation of collusive and efficiency-based synergies in horizontal mergers has proven difficult. The authors propose a theory-backed methodological approach to classify mergers that yields greater information on merger types and merger effects. Moreover, the methodological approach distinguishes between mergers characterized largely by collusion-based synergies and those characterized largely by efficiency-based synergies. Crucial to the proposed method is that it considers the impact of merger events not only on merging firms, as is common in the literature, but also on non-merging rivals. The authors demonstrate how the proposed approach clarifies the nature of merger activity through an event-study procedure based on stock market data on samples of large horizontal mergers drawn from the US and UK (an Anglo-American sub-sample) and from the European continent the authors demonstrate how the proposed schematic clarifies the nature of merger activity.