[Missing Data] Wasserstein Distributionally Robust Linear Quantile Regression on Missing Data (with Yanqin Fan and Gaoqian Xu)

This paper proposes a Distributionally Robust (DR) linear quantile estimator to handle deviations from the “Missing At Random” (MAR) assumption in incomplete data. While MAR-based estimators can perform poorly when the missingness mechanism deviates from MAR, fully assumption-free approaches yield overly conservative bounds. To address this, we introduce a distributionally robust optimization framework using the Wasserstein distance to measure departures from the MAR distribution. The estimator solves a minimax optimization problem by maximizing the worst-case expected loss over a Wasserstein ball and minimizing it with respect to the parameter of interest.