This paper discusses the antitrust reform measures taken during the occupation of Japan following the end of World War II. These antitrust reforms included the dissolution of the zaibatsu business groups and the adoption of the Antimonopoly Act. However, the trust-busting and antitrust measures taken by Japan failed to prevent the eventual rise of keiretsu business groups and lower the concentration of corporate ownership in Japan. The primary reasons behind this failure were the inability of the reformers to fully dismantle the zaibatsu business groups and the changing priorities of the reformers due to the growing threat of the spread of communism in Asia. Despite the shortcomings of the Japanese antitrust reforms, the existence of the keiretsu business groups within Japan did not prevent Japan from successfully democratizing, experiencing significant economic growth, or reducing income inequality.
