U.S. Antitrust Agencies Issue Revised Horizontal Merger Guidelines

Following a remarkably transparent process, on August 19, 2010, the United States Department of Justice and Federal Trade Commission (collectively, the "Agencies") released revised Horizontal Merger Guidelines ("Guidelines").¹ The Guidelines incorporate a number of noteworthy revisions. First, they significantly raise the concentration thresholds at which mergers warrant greater scrutiny. Second, they deemphasize the role of market definition. Third, they place greater reliance on economic models in mergers involving differentiated products.

Significant Additions and Changes to the Merger Guidelines

Significant Increase in the HHI Thresholds Used to Screen Transactions: Section 5.3 of the Guidelines significantly adjusts upward the concentration thresholds (measured by the Herfindahl-Hirschman Index, or "HHI") used to determine when mergers merit closer scrutiny. The Guidelines consider a market with an HHI below 1500 unconcentrated (an increase from 1000 in the