Each stage of merger analysis involves predictions about uncertain events. The quality of merger enforcement and its ability to improve consumer welfare depend heavily on how well the federal antitrust agencies cope with such uncertainty. The agencies and the courts have to date adopted an...

We study how the courts have responded to the 2010 Horizontal Merger Guidelines issued by the U.S. Department of Justice and the Federal Trade Commission. Looking at decided cases, we find that both the government and merging parties rely on the 2010 Guidelines in presenting their cases, each...