Double marginalization is a robust phenomenon in procurement under asymmetric information when sophisticated contracts can be implemented. In this context, vertical integration causes merger-specific elimination of double marginalization but biases the make-or-buy decision against independent suppliers. If the buyer has full bargaining power over prices and quantities, a vertical merger benefits final consumers even when it results in the exclusion of efficient suppliers. If on the contrary the buyer’s bargaining power is reduced after she has committed to deal exclusively with a limited set of suppliers, exclusion of efficient suppliers may harm final consumers.

中文翻译：

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双重边缘化、市场封锁和垂直整合

当可以执行复杂的合同时，双重边际化是信息不对称下采购中的一个严重现象。在这种情况下，垂直整合导致特定于合并的双重边缘化的消除，但使自制或外购决策偏向于独立供应商。如果买方对价格和数量拥有充分的议价能力，那么纵向合并即使会导致高效供应商被排除在外，也会使最终消费者受益。相反，如果买方在承诺与有限的一组供应商进行排他性交易后议价能力下降，那么排除高效供应商可能会损害最终消费者。