The assumption that prosperity stabilizes or reduces population is questionable whereas more people threatens the prosperity of all by reducing non-renewable resources and the biosphere that sustains life.
The assumption that development and prosperity will lower fertility is based on the demographic transition theory which however made incorrect historical assumptions about the industrialized countries of Europe where the fertility transition to small families occurred, not with economic development and prosperity as widely believed, but in the midst of desperate poverty and very high infant mortality. Western birth rates fell during the 1930’s Depression, and the post-war baby boom occurred at a time of unprecedented prosperity – both contrary to the assumptions of the demographic transition theory. Interestingly, the wealth of many oil-rich countries has not made a dent in population growth rates, e.g. Saudi Arabia grew from 3.2 m. in 1950 to 18.3 m. in 1995 and continues to increase rapidly.
In the developed world, more opportunities for women in the workforce and economic growth have in fact contributed to a reduction in birth rates. However, in the developing world, where almost all the increase in global population is occurring, a demographic transition has largely failed to take effect.
The prospect of greater prosperity pales in the face of growing environmental constraints and dwindling natural resources. Signs of human-caused environmental distress – collapsing fisheries, global warming, deforestation, and the loss of agricultural land through soil erosion and desertification – suggest that human demands greatly exceed the levels that can be supported sustainably. And, there is evidence that demand for many natural resources is beginning to exceed supply.
Population growth undermines the very resources that provide the basis of future prosperity. On a positive note, there is increasing evidence that fertility declines in developing nations do not have to be preceded by western-style industrialization. Especially in Asia and Central and South America surveys show a widespread desire for smaller families. The best way to hasten the global decline in fertility is to meet the enormous unmet demand for contraceptives.