Recovering Distributions in Difference-in-Differences Models: A Comparison of Selective and Comprehensive Schooling
利用英国国家儿童发展研究数据，比较选择性中学与非选择性中学对学生考试成绩的影响，通过推广双重差分方法识别整个反事实结果分布，发现选择性学校的优势主要源于学生构成的差异。
We compare the effects of selective and nonselective secondary education on children's test scores, using British data from the National Child Development Study. Test scores are modeled as the output of an additive production function. An important input is the child's unobserved initial endowment, which may be correlated with the education system attended. In this model, we generalize the difference-in-differences approach and identify the entire counterfactual distribution of potential outcomes. Our results suggest that the better performance of selective schools relative to nonselective ones is essentially due to differences in pupils' composition.