Endogeneity and Discrete Outcomes

This paper studies models for discrete outcomes which permit explanatory variables to be endogenous. In these models there is a single nonadditive latent variate which is restricted to be locally independent of instruments. The models are incomplete; they are silent about the nature of dependence between the latent variate and the endogenous variable and the role of the instrument in this relationship. These single equation IV models which, when an outcome is continuous, can have point identifying power, have only set identifying power when the outcome is discrete. Identi…cation regions vary with the strength and support of instruments and shrink as the support of a discrete outcome grows. The paper extends the analysis of structural quantile functions with endogenous arguments to cases in which there are discrete outcomes. Keywords: Partial identi…cation, Nonparametric methods, Nonadditive models, Discrete distributions, Ordered choice, Count data models, Endogeneity, Instrumental variables, Structural quantile functions, Incomplete models.