The Nobel laureate William Shockley controversially argued in the late 19th century that the future of the world population was threatened as people with low IQs had more children than people with higher IQs. The first studies concerned with this issue found that there is an actual negative correlation between intelligence and fertility rates. The smarter people were, the lower was their fertility. On the other side those studies also found that the survival rate among more intelligent people was higher so that the overall net effect on population was unclear. Nevertheless, assuming that the survival rate in general increases due to better living conditions, the negative correlation between intelligence and fertility suggests that the average IQ should be decreasing.
In more recent studies, scholars extended their research from only national data towards international data and used educational attainment data as proxies for intelligence. The following chart shows data provided by the World Bank to picture the correlation between fertility rates and female education.
We can see that, throughout the different regions of the world, the completion rate of primary education among women not only increased but also that the fertility rate decreased. To see the change in both variables over time please click on the picture. It suggests a clear negative correlation between education and fertility throughout the world.
But the United Nations find five different explanations that cause a decline in fertility:
1) The mortality decline in childbirth and the decline in child mortality.
2) The decline in the female age at marriage.
3) The increase in female literacy and education.
4) The female economic participation.
5) And the increased access to contraception.
The first cause implies that if more children survive, parents have less reason to have more children in order to be secured and taken care of when getting old. The second reason holds, as women getting married in a younger age will naturally be able to give birth to more children than a woman getting married later. This suggests that early childbearing can cause less education as women have less time to go to school when the first child is born. This again is directly related to the third cause. The fourth reason implies that if women have access to economic activities they will decide to have fewer children in order to gain income. And income is again related to intelligence and education.
This relationship between higher income and a decline in fertility is named the demographic-economic paradox. In the following, scholars found what is called the fertility-development controversy. We can see that there is not only a negative correlation between education and fertility but also in the Human Development Index and the fertility rate of a country.
This suggests that an increase in the standards of living reduces fertility and that education therefore seems to play an important role. But it is not clear whether or not education causes a decline in fertility or the other way round.
Written by Julia Seither
Graff, Harvey: “Literacy, Education and Fertility, Past and Present: A Critical Review”.
United Nations Report: “Completing the Fertility Transition”.
World Bank Data