The Proximal Surrogate Index: Long-Term Treatment Effects under Unobserved Confounding
近端替代指标:未观测混杂下的长期处理效应
We study the identification and estimation of long-term treatment effects under unobserved confounding by combining an experimental sample, where the long-term outcome is missing, with an observational sample, where the treatment assignment is unobserved. While standard surrogate index methods fail when unobserved confounders exist, we establish novel identification results by leveraging proxy variables for the unobserved confounders. We further develop multiply robust…