News release: “To promote transparency in merger enforcement, the Federal Trade Commission released an updated staff report on the agency’s major investigations of horizontal mergers. The update adds four more years of data to the agency’s previous report, which was issued in 2008. Horizontal mergers involve two firms that are competitors or have overlapping lines of business. The new data provide information on the levels of market concentration involved in the FTC’s investigation of 264 mergers, covering 1,372 markets over a 16-year period. The data tabulations use two statistics from the agency’s Horizontal Merger Guidelines to measure market concentration: 1) the post-merger Herfindahl-Hirschman Index (HHI), and 2) the change in the HHI, which reflects changes in market concentration before and after a particular merger. They also track the number of “significant competitors” in the markets in these cases. Data on HHIs are available for 1,359 markets and data on significant competitors are presented for 1,143 markets. The HHI reflects the overall composition of the market and the distribution of market shares of the competing firms.”