Importance sampling is a widely used variance reduction technique to compute sample quantiles such as value at risk. The variance of the weighted sample quantile estimator is usually a difficult quantity to compute. In this paper we present the exact convergence rate and asymptotic distributions of the bootstrap variance estimators for quantiles of weighted empirical distributions. Under regularity conditions, we show that the bootstrap variance estimator is asymptotically normal and has relative standard deviation of order O(n-1/4).
"The convergence rate and asymptotic distribution of the bootstrap quantile variance estimator for importance sampling." Adv. in Appl. Probab. 44 (3) 815 - 841, September 2012. https://doi.org/10.1239/aap/1346955266