"Two conclusions can be drawn from this study. First, economic models of fertility behavior that emphasize the distinctions between income and price effects - what we have called male income and female wage effects - are successful in explaining not only important features of cross-sectional variations but also aggregate movements of U.S. fertility over time. Second, the model we propose successfully predicts both procyclical and countercyclical variations in fertility in a unified framework, across age groups, and over a long time span." : - p. 326.