On the inconsistency of matching without replacement

• 成果类型: Article
• 署名作者: Savje, F.
• 署名单位: Yale University
• 刊物名称: BIOMETRIKA
• ISSN/ISSBN: 0006-3444
• DOI: 10.1093/biomet/asab035
• 发表日期: 2022
• 页码: 551558
• 关键词: propensity score; estimators; BIAS

摘要

The paper shows that matching without replacement on propensity scores produces estimators that generally are inconsistent for the average treatment effect of the treated. To achieve consistency, practitioners must either assume that no units exist with propensity scores greater than 1/2 or assume that there is no confounding among such units. The result is not driven by the use of propensity scores, and similar artifacts arise when matching on other scores as long as it is without replacement.