Horizontal Mergers: Comment
评论Farrell和Shapiro（1990a）关于横向并购的Cournot模型分析，指出其关于并购对价格和消费者福利影响的结论比以往文献更一般，并讨论了并购对非并购企业和消费者的外部福利效应。
Joseph Farrell and Carl Shapiro (1990a) present an interesting and elegant analysis of horizontal mergers in the context of a Cournot model under quite general demand and cost conditions. One section of their paper deals with the effects of mergers on price or consumer welfare. In it they show that, in a Cournot model, mergers that do not lower costs always raise price and that mergers that lower costs still raise price unless they lower costs quite a lot. These results are much more general than anything in the prior literature. Another section of the paper deals with the effects of mergers on nonmerging firms and consumers, which Farrell and Shapiro term external. With some minor additional assumptions, they show that a merger is externally welfare-enhancing if (but not only if)