  A new bandwidth selection rule that uses different bandwidths for the local
linear regression estimators on the left and the right of the cut-off point is
proposed for the sharp regression discontinuity estimator of the mean program
impact at the cut-off point. The asymptotic mean squared error of the estimator
using the proposed bandwidth selection rule is shown to be smaller than other
bandwidth selection rules proposed in the literature. An extensive simulation
study shows that the proposed method's performances for the sample sizes 500,
2000, and 5000 closely match the theoretical predictions.
