Abstract
In this article, which is part of the Symposium on the Tenth Anniversary of the 2010 Horizontal Merger Guidelines, we suggest a number of improvements that should be considered in the next revision of the Guidelines. Our analysis is based on the observation that horizontal merger policy has suffered from under-enforcement. We provide evidence that the enforcement agencies face significant resource constraints that require a triage process that inevitably leads to under-enforcement. In light of merger law placing greater weight on avoiding false negatives and under-deterrence than false positive and over-deterrence, the article suggests a number of ways in which the under-enforcement bias might be corrected, including (among others): rolling back the increase in the HHI "red zone" thresholds; mandating anticompetitive presumptions for mergers with high GUPPIs, acquisitions of mavericks, and acquisitions by dominant firms; closer analysis of common ownership by financial funds; and expanded analysis of potential competition mergers.