Subjective Beliefs and ex ante Trade
定义了一种适用于模糊性偏好的主观信念，并基于市场行为刻画了这种信念。利用该定义，推导出事前交易效率的充要条件，并证明其源于福利经济学基本定理。当不存在总体不确定性时，完全保险有效当且仅当代理人共享某些共同主观信念。结果适用于包含模糊厌恶的凸偏好函数形式。
We study a definition of subjective beliefs applicable to preferences that allow for the perception of ambiguity, and provide a characterization of such beliefs in terms of market behavior. Using this definition, we derive necessary and sufficient conditions for the efficiency of ex ante trade and show that these conditions follow from the fundamental welfare theorems. When aggregate uncertainty is absent, our results show that full insurance is efficient if and only if agents share some common subjective beliefs. Our results hold for a general class of convex preferences, which contains many functional forms used in applications involving ambiguity and ambiguity aversion. We show how our results can be articulated in the language of these functional forms, confirming results existing in the literature, generating new results, and providing a useful tool for applications. Copyright 2008 The Econometric Society.