How should a buyer design procurement mechanisms when suppliers' costs are unknown, and the buyer does not have a prior belief? We demonstrate that simple mechanisms - that share a constant fraction of the buyer utility with the seller - allow the buyer to realize a guaranteed positive fraction of the efficient social surplus across all possible costs. Moreover, a judicious choice of the share based on the known demand maximizes the surplus ratio guarantee that can be attained across all possible (arbitrarily complex and nonlinear) mechanisms and cost functions. Similar results hold in related nonlinear pricing and optimal regulation problems.

翻译：当供应商成本未知且买方缺乏先验信念时，应如何设计采购机制？我们证明，通过采用简单机制——将买方效用的恒定比例分配给卖方——买方能够在所有可能的成本条件下，确保实现有效社会剩余的正比例。此外，基于已知需求对分配比例进行审慎选择，可在所有可能的（任意复杂且非线性的）机制与成本函数中，最大化可实现的剩余比例保证。类似结论在相关的非线性定价与最优规制问题中同样成立。