Author(s)  
Dan Black
Joonhwi Joo
Robert LaLonde
Jeffrey Smith
Evan Taylor

We provide simple tests for selection on unobserved variables in the Vytlacil-Imbens-Angrist framework for Local Average Treatment Effects (LATEs). Our setup allows researchers not only to test for selection on either or both of the treated and untreated outcomes, but also to assess the magnitude of the selection effect. We show that it applies to the standard binary instrument case, as well as to experiments with imperfect compliance and fuzzy regression discontinuity designs, and we link it to broader discussions regarding instrumental variables. We illustrate the substantive value-added by our framework with three empirical applications drawn from the literature. 

Publication Type  
Working Paper
File Description  
First version, June 13, 2020
JEL Codes  
C10: Econometric and Statistical Methods and Methodology: General
D04: Microeconomic Policy: Formulation; Implementation; Evaluation
Keywords  
instrumental variables
local average treatment effect
selection
test