Abadie, Alberto; Imbens, Guido - National Bureau of Economic Research (NBER) - 2002
conditional bias term which may not vanish at a rate faster than root-N when more than one continuous variable is used for … conditional bias, matching estimators with a fixed number of matches do not reach the semiparametric efficiency bound for average … treatment effects, although the efficiency loss may be small. Third, we propose a bias-correction that removes the conditional …