Estimand of Instrumental Variable Estimator for Any Outcome and Any Heterogeneous Effect

（任意结果和任意异质效应的工具变量估计量）

主讲人：Myoung-jae Lee（Korea University）

主持老师：（北大国发院）孙振庭

参与老师：（北大经院）王一鸣、王熙、刘蕴霆、王法

（北大国发院）沈艳、黄卓、张俊妮

（北大新结构）胡博

时间：2023年11月1日（周三） 10:00-11:30

地点（线下）：北京大学国家发展研究院承泽园院区131教室

报告摘要：

For a binary treatment D, an outcome Y and covariates X, a linear model with a constant treatment effect is widely used, but the linear model is untenable if Y is a limited dependent variable (LDV) with a continuous covariate. Despite this problem, motivations to use a linear model are strong when D is endogenous, because dealing with a binary endogenous D and a LDV Y is particularly difficult unless a fully parametric approach is adopted. Hence, practitioners often apply instrumental variable estimator (IVE) to a linear model with a LDV Y. In this paper, firstly, we show that IVE with a binary instrument Z for D estimates a 'weighted average of X-heterogeneous effects on compliers' plus a bias term, where the bias is not zero in general unless a restrictive condition is met. Secondly, the bias can be reduced much by specifying the X-part in the linear model such that the X-part explains Z well, not necessarily Y. Thirdly, a modified IVE using the 'instrument residual' instead of Z has zero bias without the restrictive condition. An empirical analysis is provided to demonstrate these points.

主讲人简介：

Professor Myoung-jae Lee is an econometrician/statistician in Korea University. He held regular positions in many universities around the world, including Penn State, Tilburg University, Chinese University of Hong Kong, and Australian National University. He published six single-authored books on micro-econometrics and treatment effect analysis, and more than 90 papers in SCI/SSCI-listed journals on economics, statistics, transportation, medicine, sociology and political science.