Effects of antitrust enforcement on aggregate concentration

Four indexes are employed to measure trends in asset concentration of large business in the United States between 1967 and 1992 using the Fortune 500 data. The paper also investigates whether the merger wave of the 1980s was statistically significant. For all the 500 and the top 100 firms, each of the indexes confirmed that concentration trends were on the increase for the whole period and that the increase in the level of concentration due to the mergers of the 1980s was statistically significant. However, on both counts, not all indexes were in agreement for the bottom 300 firms when examined by subsets of 100 firms.