Estimating Self‐Selection in Medicare Advantage
利用65岁初始参保期的准实验变化，基于2007-2017年行政索赔数据，检验商业保险参保者转入医疗保险优势计划时的自选择现象，发现参保者在健康状况上存在有利选择。
ABSTRACT We explore the fundamental question of selection in Medicare Advantage by exploiting quasi‐experimental variation from the Initial Enrollment Period for Medicare eligibility to evaluate and describe participation in Medicare Advantage. Using administrative claims data between 2007 and 2017, we investigate the transition from commercial insurance to Medicare Advantage for a comprehensive subset of commercially insured enrollees. We use the sharp cutoff at age 65 in one of the largest commercial and Medicare Advantage databases in the United States to implement a “positive correlation” test. Our findings using baseline characteristics at age 64 reveal that enrollees in Medicare Advantage are advantageously selected on multiple measures of health status such as Charlson Comorbidity Index (CCI) scores, out‐of‐pocket costs, utilization, while differentially selected on demographic characteristics. Furthermore, using predicted Medicare Advantage utilization based on observable characteristics, we find even stronger evidence of advantageous selection, suggesting that observable characteristics at age 64 systematically predict which enrollees would benefit most from Medicare Advantage's features, indicating forward‐looking selection behavior.