Published online by Cambridge University Press: 01 June 2009
Consider the unconditional moment restrictionE[m(y,υ, w;π0)/fV|w(υ|w)−s (w;π0)] = 0, wherem(·) and s(·) are knownvector-valued functions of data(y┬, υ,w┬)┬. Thesmallest asymptotic variance that -consistent regularestimators ofπ0 canhave is calculated whenfV|w(·)is only known to be a bounded, continuous, nonzeroconditional density function. Our results show that“plug-in” kernel-based estimators ofπ0constructed from this type of moment restriction,such as Lewbel (1998, Econometrica66, 105–121) and Lewbel (2007, Journal ofEconometrics 141, 777–806), aresemiparametric efficient.
We thank the co-editor Richard Smith, twoanonymous referees, Francesco Bravo, Juan CarlosEscanciano, Javier Hidalgo, Kim Huynh, OliverLinton, and Pravin Trivedi for many helpfulcomments, corrections, and suggestions. The usualdisclaimers apply.