Semiparametric efficiency bounds

Abstract Semiparametric models are those where the functional form of some components is unknown. Efficiency bounds are of fundamental importance for such models. They provide a guide to estimation methods and give an asymptotic efficiency standard. The purpose of this paper is to provide an introduction to research methods and problems for semiparametric efficiency bounds. The nature of the bounds is discussed, as well as ways of calculating them. Their uses in solving estimation problems are outlined, including construction of semiparametric estimators and calculation of their limiting distribution. The paper includes new results as well as survey material.