There have been two periods of intense interest in the determinants of fertility by demographers. The first period, which encompasses the late nineteenth and early twentieth centuries, was dominated by a concern about differential fertility within Western countries; in this period, leaders of the eugenics movement enlisted the services of demographers to learn how these differentials could be reduced, either by increasing the fertility of some groups or lowering the fertility of others. The second period, encompassing the 1940s to the late 1980s, was dominated by concern about differences in fertility (and thus in population growth rates) between Western countries and those countries known variously as, "less developed," "developing," "Third World," and, most recently, "Southern." In this period, there was little effort to raise fertility in low-fertility societies but a great deal of effort by an international population movement composed of neo-Malthusians and family planners to...