We extend PML theory to account for information on the conditional moments up to order four, but without assuming a parametric model, to avoid a risk of misspecification of the conditional distribution. The key statistical tool is the quartic exponential family, which allows us to generalize the...

This paper presents two alternative formulations of the instrumental variables (IV) procedure. One of the formulations, termed the "completed model", serves to show, in a general way, that the IV estimator of a vector of regression parameter is asymptotically as efficient as the maximum...