This study examines how antitrust law adoptions affect horizontal merger and acquisition (M&A) outcomes. Using the staggered introduction of competition laws in 20 countries, we find antitrust regulation decreases acquirers’ five-day cumulative abnormal returns surrounding horizontal merger...

The legality of a horizontal merger under section 7 of the Clayton Act turns on a reckoning of its social costs and benefits. This paper reviews what economics has to say about that reckoning and explores the relationship between economic learning and merger law and policy