Inverse probability weighted estimation of local average treatment effects: A higher order MSE expansion

•Propose a modified inverse probability weighted estimator for LATE.•Use local polynomial regression to estimate the instrument propensity score.•The modified estimator remains asymptotically normal and efficient.•Provide a higher order expansion of its asymptotic mean squared error.

We consider a new inverse probability weighted estimator for the local average treatment effect parameter where the instrument propensity score is estimated by local polynomial regression. We derive its asymptotics and provide a higher order expansion of its asymptotic MSE.