This book consists of three essays on M&A-related antitrust regulations  in Korea. A comparative study of market concentration measures, which appear in merger guidelines, is carried out.

The first essay (Chapter 2) compares different market concentration indices, namely the Herfindahl (H) index and several CRk indices including CR3. In terms of market structure information and theoretical justification, the H index is believed to be superior to other traditional measures. In an empirical test using Korean market data, however, we can not conclude that the former outperforms the latter significantly in predicting inter-market differences in the profit-to-sales ratio. After a comprehensive comparison, we conclude that the H index would be better suited in the merger guideline of Korea. 

The second essay (Chapter 3) carries out a policy simulation on the merger guidelines of the U. S., Korea, and Japan. The strictness of the market concentration threshold, above which a merger may be subject to antitrust challenge, are compared in those countries. In terms of the threshold itself, Japan has the strictest one, followed by the U. S. Korea has the most lenient one. But, in terms of legal enforcement, Japan has fewest cases of having blocked M&As under antitrust regulations.

Korea is not so different from Japan in that respect. only three cases of M&As have been blocked by the Fair Trade Commission during  1981-1997 out of 3,760 total cases. In other words, it can be said that there exists a huge gap between legal rules and their enforcement. Neither country uses the market concentration index as a threshold test at their early stage when evaluating M&As. 

on the other hand, the U. S. has developed and refined a merger guideline, to be well-equipped in theory and practice. The guideline(1992) is not merely a cosmetic measure, but  an actively enforced rule.

In Korea, efforts to screen out risky mergers should be stepped up. To do so, antitrust authorities must have stronger authority and wider support for implementing the competition policy and as a result be able to enforce the rules.

As a concluding one, the third essay(Chapter 4) suggests a list of findings and policy implications, derived from studies of merger guidelines in Korea and other countries.