There are many economic parameters that depend on nonparametric ﬁrst steps. Examples include games, dynamic discrete choice, average exact consumer surplus, and treatment eﬀects. Often estimators of these parameters are asymptotically equivalent to a sample average of an object referred to as the inﬂuence function. The inﬂuence function is useful in local policy analysis, in evaluating local sensitivity of estimators, and constructing debiased machine learning estimators. We show that the inﬂuence function is a Gateaux derivative with respect to a smooth deviation evaluated at a point mass. This result generalizes the classic Von Mises (1947) and Hampel (1974) calculation to estimators that depend on smooth nonparametric ﬁrst steps. We give explicit inﬂuence functions for ﬁrst steps that satisfy exogenous or endogenous orthogonality conditions. We use these results to generalize the omitted variable bias formula for regression to policy analysis for and sensitivity to structural changes. We apply this analysis and ﬁnd no sensitivity to endogeneity of average equivalent variation estimates in a gasoline demand application.