This paper demonstrates the extensive scope of an alternative to standardinstrumental variables methods, namely covariate-based methods, for identifying and es-timating effects of interest in general structural systems. As we show, commonly usedeconometric methods, speci…cally parametric,...

We give two new approaches to testing a conditional form of exogeneity. This conditionensures unconfoundedness and identication of eects of interest in structural systems. Asthese approaches do not rely on the absence of causal eects of treatment under the null,they complement earlier methods of...