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A Meta-Study of Merger Retrospectives in the United States

Over the last decade, merger retrospectives have become increasingly popular. However, it is far from clear what implications can be drawn from these analyses, because the results suffer from a sample selection problem. This paper uses models of the Federal Trade Commission’s enforcement activity to estimate challenge probabilities and address the selection issue. Although the small size of the meta-study panel limits the statistical interpretation of the results, general observations are possible. First, significant price effects appear in the matters with very high challenge probabilities. When challenge probabilities are moderate, roughly 30-60 percent, retrospective results generate price effects in half the studies. For low challenge probabilities, no price effects are observed in the retrospectives related to collusion theories. Positive effects are noted for retrospectives in some consumer goods markets, but theoretical analysis implies these results are questionable. Although retrospectives, interpreted in light of the likely competitive concern, can serve as a test for merger policy, policy predictions also serve as a test of the credibility of the retrospectives.