||This article possibly contains original research. (August 2015)|
The demographic-economic "paradox" is the inverse correlation found between income and fertility within and between nations. The higher the degree of education and GDP per capita of a human population, subpopulation or social stratum, the fewer children are born in any industrialized country. In a 1974 UN population conference in Bucharest, Karan Singh, a former minister of population in India, illustrated this trend by stating "Development is the best contraceptive."
The term "paradox" comes from the notion that greater means would enable the production of more offspring as suggested by the influential Thomas Malthus. Roughly speaking, nations or subpopulations with higher GDP per capita are observed to have fewer children, even though a richer population can support more children. Malthus held that in order to prevent widespread suffering, from famine for example, what he called "moral restraint" (which included abstinence) was required. The demographic-economic paradox suggests that reproductive restraint arises naturally as a consequence of economic progress.
It is hypothesized that the observed trend in many countries of having fewer children has come about as a response to increased life expectancy, reduced childhood mortality, improved female literacy and independence, and urbanization that all result from increased GDP per capita, consistent with the demographic transition model.
According to the UN, "[a]mong the 201 countries or areas with at least 90,000 inhabitants in 2013, 50 countries in 1990-1995 and 71 countries in 2005-2010 had below-replacement fertility. In 2005-2010, 27 countries had very low fertility, below 1.5 children per woman, and all of these countries are located in Eastern Asia or Europe." 
Religious societies tend to have higher birth rates than secular ones, and richer, more educated nations tend to advance secularization. This may help explain the Israeli and Saudi Arabian exceptions, the two notable outliers in the graph of fertility versus GDP per capita at the top of this article.
The role of different religions in determining family size is complex. For example, the Catholic countries of southern Europe traditionally had a much higher fertility rate than was the case in Protestant northern Europe. However, economic growth in Spain, Italy, Poland etc., has been accompanied by a particularly sharp fall in the fertility rate, to a level below that of the Protestant north. This suggests that the demographic-economic paradox applies more strongly in Catholic countries, although Catholic fertility started to fall when the liberalizing reforms of Vatican II were implemented. It remains to be seen if the fertility rate among (mostly Catholic) Hispanics in the U.S. will follow a similar pattern.
A reduction in fertility can lead to an aging population which leads to a variety of problems, see for example the Demographics of Japan.
A related concern is that high birth rates tend to place a greater burden of child rearing and education on populations already struggling with poverty. Consequently, inequality lowers average education and hampers economic growth. Also, in countries with a high burden of this kind, a reduction in fertility can hamper economic growth as well as the other way around.
A study in France came to the result that employment instability has a strong and persistent negative effect on the final number of children for both men and women, and contributes to fertility postponement for men. It also came to the result that employment instability has a negative influence on fertility among those with more egalitarian views about the division of labor, but still a positive influence for women with more traditional views.
Some scholars have recently questioned the assumption that economic development and fertility are correlated in a simple negative manner. A study published in Nature in 2009 has found that when using the Human Development Index instead of the GDP as measure for economic development, fertility follows a j-shaped curve: with rising economic development, fertility rates indeed do drop at first, but then begin to rise again as the level of social and economic development increases, while still remaining below the replacement rate
In an article published in Nature, Myrskylä et al. pointed out that “unprecedented increases” in social and economic development in the 20th century had been accompanied by considerable declines in population growth rates and fertility. This negative association between human fertility and socio-economic development has been “one of the most solidly established and generally accepted empirical regularities in the social sciences”. The researchers used cross-sectional and longitudinal analyses to examine the relationship between total fertility rate (TFR) and the human development index (HDI).
The main finding of the study was that, in highly developed countries with HDI above 0.9, further development halts the declining fertility rates. This means that the previously negative development-fertility association is reversed; the graph becomes J-shaped. Myrskylä et al. contend that there has occurred “a fundamental change in the well-established negative relationship between fertility and development as the global population entered the twenty-first century”.
Some researchers doubt J-shaped relationship fertility and socio-economic development (Luci and Thevenon, 2010; Furuoka, 2009). For example, Fumitaka Furuoka (2009) employed a piecewise regression analysis to examine the relationship between total fertility rate and human development index. However, he found no empirical evidence to support the proposition that advances in development are able to reverse declining fertility rates.
More precisely, the empirical findings of Furuoka’s 2009 study indicate that in countries with a low human development index, higher levels of HDI tend to be associated with lower fertility rates. Likewise, in countries with a high human development index, higher levels of HDI are associated with lower fertility rates, although the relationship is weaker. Furuoka's findings support the "conventional wisdom" that higher development is consistently correlated with lower overall fertility.
- Advanced maternal age
- Aging of Europe
- Aging of Japan
- Demographic economics
- Fertility and intelligence
- Total fertility rate
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