ESTIMATION OF TREATMENT EFFECTS WITHOUT AN EXCLUSION RESTRICTION: WITH AN APPLICATION TO THE ANALYSIS OF THE SCHOOL BREAKFAST PROGRAM
针对缺乏排除限制条件时难以识别因果效应的问题，提出两种新估计量，并用模拟数据比较其与现有方法的优劣；应用于学校早餐计划发现，纠正选择偏差后该计划可能降低儿童肥胖。
SUMMARY The increase in childhood obesity has garnered the attention of many in policymaking circles. Consequently, school nutrition programs such as the School Breakfast Program (SBP) have come under scrutiny. The identification of the causal effects of such programs, however, is difficult owing to non‐random selection into the program and the lack of exclusion restrictions. Here, we propose two new estimators aimed at addressing this situation. We compare our new estimators to existing approaches using simulated data. We show that while correlations might suggest that SBP causes childhood obesity, SBP is likely to reduce childhood obesity once selection is addressed. Copyright © 2012 John Wiley & Sons, Ltd.