Concentration Thresholds for Horizontal Mergers
研究了美国横向并购指南中基于集中度的阈值，发现理论上和实证上都应只关注集中度变化而非水平，并指出现有阈值可能过于宽松，除非预期效率提升5%以上或其他因素能显著约束市场力量。
Concentration-based thresholds for horizontal mergers, such as those in the US Horizontal Merger Guidelines, play a central role in merger analysis but their basis remains unclear. We show that there is both a theoretical and an empirical basis for focusing solely on the change in concentration, and ignoring its level, in screening mergers for whether their unilateral price effects will harm consumers. We also argue that current threshold levels likely are too lax, unless one expects efficiency gains of 5 percent or greater, or other factors such as entry and product repositioning to significantly constrain the exercise of market power postmerger.