Horizontal Merger Antitrust Enforcement: Some Historical Perspectives, Some Current Observations

The DOJ-FTC Merger Guidelines were developed for and best deal with horizontal mergers where the theory of harm is coordinated effects. The Guidelines deal awkwardly, at best, with mergers where the theory of harm is unilateral effects. The broad body of evidence - from profitability studies, from pricing studies, and from auction studies - indicates that seller concentration matters. But these studies do not provide adequate guidance as to whether current antitrust enforcement is too strict or too lenient with respect to mergers. Research on the consequences of the close call mergers that were not challenged might well provide such guidance, as might a meta analysis of the extant price-concentration studies. New procedures are needed for inquiry and enforcement where the theory of harm is unilateral effects, as is a market definition paradigm for monopolization cases.