Symmetrically normalized instrumental-variable estimation using panel data

Abstract

We discuss the estimation of linear panel-data models with sequential moment restrictionsu sing symmetricallyn or malizedg eneralized method of moments( GMM) estimators( SNM)and limited information maximuml i kelihood( LIML)analogues These es imators are asymptotically equivalent to standardG MMb ut are invariantto normalizationan dt end to havea smallerf inite-samplbe ias, especiallyw hen the instruments are poor. We study their properties in relation to ordinary GMM and minimum distancee stimators for AR(1)model swith individual effects by mean of simulations. Finally, as empirical ilustrations, we estimate by SNM and LML employment and wage equations using panels of U.K. and Spanish firm.