Bounded, Efficient and Triply Robust Estimation of Average Treatment Effects Using Instrumental Variables

• Activity Number: 619 - Causal Inference in Biometric Data
• Type: Contributed
• Date/Time: Thursday, August 3, 2017 : 8:30 AM to 10:20 AM
• Sponsor: Biometrics Section
• Author(s): Linbo Wang* and Eric Tchetgen Tchetgen
• Companies: University of Washington and Harvard University
• Keywords: Binary outcome ; Causal inference ; Identification ; Semiparametric inference ; Unmeasured confounding

Abstract

Instrumental variables (IVs) are widely used for estimating causal effects in the presence of unmeasured confounding. Under the standard IV model, however, the average treatment effect (ATE) is only partially identifiable. To address this, we propose novel assumptions that allow for identification of the ATE. Our identification assumptions are clearly separated from model assumptions needed for estimation, so that researchers are not required to commit to a specific observed data model in establishing identification. We then construct multiple estimators that are consistent under three different observed data models, and triply robust estimators that are consistent in the union of these observed data models. We pay special attention to the case of binary outcomes, for which we obtain bounded estimators of the ATE that are guaranteed to lie between -1 and 1. Our approaches are illustrated with simulations and a data analysis evaluating the causal effect of education on earnings.