The Use of Stock Market Returns in Antitrust Analysis of Mergers

One of the most promising recent innovations in merger analysis has been the attempt to predict the effects of horizontal mergers by examining the share prices of the rivals to the merging firms. In this paper we describe the standard procedure, discuss some of the major criticisms of that procedure, and propose a modification, apply it to a sample of recent mergers, contrast the results with those from the standard procedure, and discuss the appropriate uses and remaining limitations of the model for antitrust analysis.