Code for: Concentration Thresholds for Horizontal Mergers

Concentration-based thresholds for horizontal mergers, such as thosein the U.S. DOJ/FTC Horizontal Merger Guidelines, play a centralrole in merger analysis but their basis remains unclear. We study, both theoretically and empirically,the extent to which the level of concentration, and the merger-induced change in concentration, are helpful in screening mergers for whether theirunilateral price effects will harm consumers.