Family Size of Children and Women during the Demographic Transition

David Lam, University of Michigan
Leticia J. Marteleto, University of Michigan

In this paper we analyze the links between declines in fertility and declines in the family size of school-aged children during the demographic transition. We extend Preston’s (1976) model to analyze family size from the perspective of children of a given age rather than women of a given age. This complicates the analytical model, but we show that the key insights of Preston’s results still hold. The mean family size of school-aged children can be approximated by a simple function of the mean and coefficient of variation of fertility for women born 15-40 years earlier. We apply the framework to micro-census data from Brazil, Kenya, Mexico and Vietnam, and demonstrate that the model provides a good approximation to actual family size. Because there is often a compression of fertility coinciding with rapid decline in the mean, the mean family size experienced by school-aged children often falls faster than fertility.