(January 31, 2013) -- The FTC released a staff report that updates its major investigations of horizontal mergers by adding four more years of data to the agency’s previous report which was released in 2008. Horizontal mergers involve two firms that compete against each other or have overlapping lines of business. The new information shows the levels of market concentration in the FTC’s investigation of 264 mergers in 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. The data also reflects the number of “significant competitors” in the markets in the cases. Data on Herfindahl-Hirschman Index in 1,359 markets are available and data on significant competitors also are detailed for 1,1,43 markets....