中文摘要：

考虑由一个供应商和两个零售商组成的二级供应链，假设产品的市场需求分布未知，供应链中的上下游企业共享需求信息．由于需求信息在供应商处汇聚，供应商与零售商占有的信息量不同，这就可能扭曲供应商对市场需求的认识，造成供应商认为市场过度膨胀或萎缩，把这种现象称为信息汇聚效应（PIE，pooled information effect）．文中首先给出PIE效应的定义，然后根据可观察需求信息的类型分两种情况讨论：对需求信息可完全观察的情况，简要给出了多周期供应链发生PIE效应的充分条件；对需求信息可部分观察的情况，基于需求信息可观察时的结论，先给出了短视订货策略下，多周期供应链发生PIE效应的充分条件，再给出了最优订货策略下，3周期供应链发生PIE效应的充分条件．数值算例和模拟实验表明，在一定条件下，发生PIE效应的概率很可观．最后分析了牛鞭效应、信息共享和信息汇聚效应的关系．

英文摘要：

This paper considers a two-stage supply chain consisting of a supplier and two retailers and assumes that the demand distribution is unknown and that there is information sharing in supply chains, since the demand information is pooled at the supplier, the supplier and the retailers will obtain different information, which may lead the supplier to think the market has expanded or shryink too much. We call this phenomenon Pooled Information Effect （PIE）. To analyze conditions for PIE, two cases are discussed. In the case of fully observable demand information, we present the sufficient condition for PIE in multi-period supply chains. In the case of partially observable demand information, we present the sufficient condition for PIE in multi-period supply chains when the myopic inventory strategy is adopted and that in a three-period supply chain when optimal inventory strategy is adopted. Numerical examples and simulations show that the probability of PIE is considerably greater under certain conditions. Finally, we analyze the relationship among the bullwhip effect, information sharing and pooled information effect.