Fertility and Childlessness in the United States
构建了一个区分生育密集边际与广泛边际的理论，利用1990年美国人口普查数据识别深层参数，发现2.5%的女性因贫困无子女，8.1%因育儿机会成本过高，并解释了无子女率随全要素生产率和教育变化的U型趋势。
We develop a theory of fertility, distinguishing its intensive margin from its extensive margin. The deep parameters are identified using facts from the 1990 US Census: (i) fertility of mothers decreases with education; (ii) childlessness exhibits a U-shaped relationship with education; (iii) the relationship between marriage rates and education is hump-shaped for women and increasing for men. We estimate that 2.5 percent of women were childless because of poverty and 8.1 percent because of high opportunity cost of childrearing. Over time, historical trends in total factor productivity and in education led to a U-shaped response in childlessness rates while fertility of mothers decreased.