The Supreme Court recognized that t

The Supreme Court recognized that the structure of an industry was also affected by mergers Section 7 of the Clayton Act and the Celler-Kefauver Act prohibit mergers that “substantially lessen competition “ or tend to lend to monopoly. According to its 1984 guidelines, the justice Department did not usually challenge a horizontal merger (i. e., a merger of firms in the same product line) during the 1980s and early 1990s if the post merger Herfindahl index (defined in Section 9-1) was less than 1,000. If the postmerger index was between 1,000 and 1,800 and the increase in the index as a result of the merger was less than 100 points, the merger usually also went unchallenged. But if the postmerger index was between 1,000 and 1,800 and the merger led to an increase in the of more than 100 points, or if the postmerger index was more than 1,800 and the merger led to an increase in the index of more than 50 points, the Justice Department was likely to challenge the merger.