Discussion on "Instrumental variable estimation of the causal hazard ratio," by Linbo Wang, Eric Tchetgen Tchetgen, Torben Martinussen, Stijn Vansteelandt.

Wang, et al.'s estimator for causal hazard ratios for endogenous treatments makes an important addition to a researcher's toolkit for analyzing censored duration outcomes. Their method complements existing methods in the semiparametric treatment effects literature and suggests useful avenues for future research.