Fertility and Intelligence - International Research

International Research

Although much of the research into intelligence and fertility has been restricted to individuals within a single nation (usually the United States), Steven Shatz (2008) extended the research internationally; he finds that "There is a strong tendency for countries with lower national IQ scores to have higher fertility rates and for countries with higher national IQ scores to have lower fertility rates."

Lynn and Harvey (2008) found a correlation of −0.73 between national IQ and fertility. They estimated that the effect had been "a decline in the world's genotypic IQ of 0.86 IQ points for the years 1950–2000. A further decline of 1.28 IQ points in the world's genotypic IQ is projected for the years 2000–2050." In the first period this effect had been compensated for by the Flynn effect causing a rise in phenotypic IQ but recent studies in four developed nations had found it has now ceased or gone into reverse. They thought it probable that both genotypic and phenotypic IQ will gradually start to decline for the whole world.

As nations with higher IQ scores have access to more resources, and thus, prophylactics and fertility education, than nations with lower IQ scores, the birth rate would be expected to be lower. Meisenberg (2009) found that both GDP and intelligence independently decrease fertility. Liberal democracy had only a weak and inconsistent effect. Furthermore, "At present rates of fertility and mortality and in the absence of changes within countries, the average IQ of the young world population would decline by 1.34 points per decade and the average per capita income would decline by 0.79% per year."