Mergers and the Value of Antitrust Deterrence
利用加拿大过去宽松的反垄断环境，检验美国严格的反垄断政策是否有效威慑了潜在合谋性并购。通过比较美加并购样本，发现市场力量假说被拒绝，表明实际上没什么可威慑的。
While the U.S. has pursued a vigorous antitrust policy towards horizontal mergers over the past four decades, mergers in Canada have until recently been permitted to take place in a virtually unrestricted antitrust environment. The absence of an antitrust overhang in Canada presents an interesting opportunity to test the conjecture that the rigid market share and concentration criteria of the U.S. policy effectively deters a significant number of potentially collusive mergers. The effective deterrence hypothesis implies that the probability of a horizontal merger being anticompetitive is higher in Canada than in the U.S. However, parameters in cross-sectional regressions reject the market power hypothesis on samples of both U.S. and Canadian mergers. Judging from the Canadian evidence, there simply isn't much to deter.