Human Capital, Fertility, and Economic Growth
假设生育率内生，且人力资本回报率随其存量上升而提高。人力资本稀缺时，家庭偏好多生育、少投资；丰富时则相反，导致两种稳定状态：大家庭低人力资本，或小家庭高人力资本。
Our analysis of growth assumes endogenous fertility and a rising rate of return on human capital as the stock of human capital increases. When human capital is abundant, rates of return on human capital investments are high relative to rates of return on children, whereas when human capital is scarce, rates of return on human capital are low relative to those on children. As a result, societies with limited human capital choose large families and invest little in each member; those with abundant human capital do the opposite. This leads to two stable steady states. One has large families and little human capital; the other has small families and perhaps growing human and physical capital.