The Effects of Birth Inputs on Birthweight
利用州级面板数据，通过分位数回归方法控制母亲不可观测异质性，估计吸烟、产前检查等变量对出生体重整个分布的影响。
Unobserved heterogeneity among childbearing women makes it difficult to isolate the causal effects of smoking and prenatal care on birth outcomes (such as birthweight). Whether a mother smokes, for instance, is likely to be correlated with unobserved characteristics of the mother. This article controls for such unobserved heterogeneity by using state-level panel data on maternally linked births. A quantile-estimation approach, motivated by a correlated random-effects model, is used to estimate the effects of smoking and other observables (number of prenatal-care visits, years of education, and so on) on the entire birthweight distribution.