Identification in Differentiated Products Markets
综述了差异化产品需求（及供给）模型中识别问题的近期研究，指出识别主要依赖工具变量而非参数假设，并讨论了工具变量类型、个体数据的作用及寡头竞争模型区分的新结果，为应用研究提供指导。
Empirical models of differentiated products demand (and often supply) are widely used in industrial organization and other fields of economics. We review some recent work studying identification in a broad class of such models. This work shows that the parametric functional forms and distributional assumptions commonly used for estimation are not essential for identification. Rather, identification relies primarily on the standard requirement that instruments be available for the endogenous variables—here, typically, prices and quantities. We discuss the types of instruments that can suffice, as well as how instrumental variables requirements can be relaxed by the availability of individual-level data or through restrictions on preferences. We also review new results on discrimination between alternative models of oligopoly competition. Together, these results reveal a strong nonparametric foundation for a broad applied literature, provide practical guidance for applied work, and may suggest new approaches to estimation and testing.