中文摘要：

在横向并购评估审查中，反垄断当局往往采用一些结构类指标作为门槛值对并购进行初步筛选，自动接受一些低于低水平门槛值且对竞争没有损害的并购．自动拒绝一些高于高水平门槛值并明显具有反竞争效应的并购。同时．对处于二者之间的并购启动效率抗辩评估审查，将并购可能产生的效率效应与反竞争效应进行权衡比较。在效率抗辩中，反垄断当局需要计算实际效率与最低要求效率（MREs），并权衡比较二者的大小，作为司法判定的主要依据。最低要求效率就是能够保证一项并购不会产生价格上涨效应的最低效率，或者说是能够抵消市场势力效应、降低价格或保持价格不上涨的成本节约的最低程度。最低要求效率是并购评估审查中效率抗辩的一项基准指标．可以作为判断并购是否具有反竞争效应的一项依据。本文从价格下降的视角分析了最坏情境下的最低要求效率．联系具体竞争模型推导了最低要求效率的测算公式和模拟分析方法．并讨论了并购可能产生的正外部效应对评估审查中最低要求效率的影响。

英文摘要：

The antitrust authorities tend to adopt some structural indicators as the preliminary screening of mergers and accept automatically some mergers which are lower than the low-level threshold and no harm to the competitive, reject automatically some mergers which are higher than the high-level threshold and have clearly anti-competitive effects. Then the antitrust authorities allow the mergers which are between low-level threshold and the high-level threshold to start an efficiency defense anff tradeoff the efficiency effect and anti-competitive effects that may arise from the merger. In the efficiency defense, the antitrust authorities need to distinguish and calculate the value of actual efficiencies and the minimum requirements efficiencies （MREs）, and compare their sizes. The paper analyzed the MREs in the worst-case scenario from the perspective of falling price, deduced the calculation formula and simulation methods of the MREs contacting the specific competition model, and discussed the effects which may generated from positive external effects on the MREs in the assessment review of mergers.