Inconvenient truths on merger retrospective studies

Abstract

Inconvenient truths prevent econometric merger retrospective studies from substantially altering our understanding of competitive effects from horizontal mergers. Econometrics cannot definitively determine the effects of particular mergers, and if they could, econometric merger retrospectives could not provide enough evidence to ground merger assessments in data on actual merger effects rather than in economic theory and legal presumptions. If merger retrospectives are to have some prospect of recalibrating merger enforcement, they must be transformed from econometric exercises into case studies examining the details of the relevant agency's assessment, but inconvenient truths likely prevent much from being learned through even such studies.