Working Paper

Control variables, discrete instruments, and identification of structural functions


Whitney K. Newey, Sami Stouli

Published Date

18 September 2018


Working Paper (CWP55/18)

Control variables provide an important means of controlling for endogeneity in econometric models with nonseparable and/or multidimensional heterogeneity. We allow for discrete instruments, giving identication results under a variety of restrictions on the way the endogenous variable and the control variables affect the outcome. We consider many structural objects of interest, such as average or quantile treatment effects. We illustrate our results with an empirical application to Engel curve estimation.