Before revision:  In sharp contrast with other methods that balance only some specific moments of covariates, the IPS aims to balanceall functions of covariates. Further, the IPS estimator is data-driven, does not rely on tuning parameters such as bandwidths, admits an asymptotic linear representation, and is \sqrt{n .
After revision:  In sharp contrast with other methods that balance only some specific moments of covariates, the IPS aims to balanceall , are data-driven, does not rely on tuning parameters such as bandwidths, admits an asymptotic linear representation, and is \sqrt{n .