In recent years there has been a marked increase in interest in the empirical evaluation of competition policy generally and merger policy more specifically. This greater interest in actual decision making in merger control proceedings has made researchers much more aware of many aspects of mergers that have not played a role in the classic theoretical treatments of the subject by Salant, Switzer and Reynolds [1983], Farrell and Shapiro [1990], and Kamien and Zang [1990]. Modern merger policy consists decreasingly in simple up or down decisions on the proposed merger as considered in this literature. Increasingly, policy intervention imposes remedies instead of outright prohibitions. Merger activity is further shaped by self-selection on the participating firms that believe their merger can pass scrutiny and generates sufficient benefits to brave the regulatory process. Increasingly, firms adjust the initial structuring of mergers and merger partners in order to satisfy anticipated regulatory concerns. In addition, we have seen instances in which merger decisions have taken into account anticipated future transactions, potential entry and other assessments of counterfactuals by the competition authorities. Furthermore, there have been lively discussions in recent years as to whether competition policy should be less lenient in macro-economically difficult times.