The revised merger guidelines, which took effect in December 2012, reinforced the standard to estimate the adverse competitive effect which is commonly applicable to various types of mergers. For instance, the revision created an independent chapter for the factors mitigating anti-competitive effect of mergers which were previously dealt with under the chapter for horizontal mergers. But, at the same time, the guidelines has endeavored to accommodate the recent developments on merger analysis which are specific to each type of mergers as follows. First, concerning horizontal mergers, the guidelines presents the standards of merger analysis that accommodate recent development in the methodology to estimate unilateral effect in differentiated markets, such as natural experiment, diversion ratio and merger simulation. And, about the coordinated effect, the guidelines recognize that a merger with a maverick could generate coordinated effect. Second, concerning vertical mergers, the guidelines consider foreclosure effect, including both input foreclosure and customer foreclosure, and coordinated effect. Third, concerning conglomerate mergers, the guidelines take into consideration overall effects on competition, such as harms to potential competition, exclusion of competitors and increase in entry barriers. Although the improvement of the merger guidelines thus far has been quite successful in accommodating recent developments in this area, there still is some room for further improvement to reflect state of the art methodologies in merger analysis. For example, the US horizontal merger guidelines were amended recently to reduce the weight of market definition and concentration ratio in merger analysis and open the door to a variety of new methodologies to directly estimate the adverse competitive effect of mergers. The US guidelines also take into consideration the effect of mergers on innovation.