local and marginal treatment effects. First, we characterize the bias, due to the omitted variables U, of (nonparametric …) regression and instrumental variables estimands, thereby generalizing the classic linear regression omitted variable bias formula … analysis. After discussing estimation and inference, we apply this framework to study earnings equations. …

instrument enables one to estimate the confounding endogeneity bias. This bias can then be utilized in subsequent regressions … apply the approach to estimate sheepskin effects. We find the bias to be approximately equal to the OLS coefficient, meaning … estimate causality. Further, one potentially can use both the conventional instrumental variable approach in tandem with our …