Structural Equations, Treatment Effects, and Econometric Policy Evaluation1
用边际处理效应统一了处理效应的非参数文献与结构估计的计量文献，从共同半参数形式生成多种处理效应，并探讨常用估计量回答的政策问题。
This paper uses the marginal treatment effect (MTE) to unify the nonparametric literature on treatment effects with the econometric literature on structural estimation using a nonparametric analog of a policy invariant parameter; to generate a variety of treatment effects from a common semiparametric functional form; to organize the literature on alternative estimators; and to explore what policy questions commonly used estimators in the treatment effect literature answer. A fundamental asymmetry intrinsic to the method of instrumental variables (IV) is noted. Recent advances in IV estimation allow for heterogeneity in responses but not in choices, and the method breaks down when both choice and response equations are heterogeneous in a general way. Copyright The Econometric Society 2005.