"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."[23]"
"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."[25]"
Thanks for the link to Wikipedia, which I help edit, but you have to know that all the Wikipedia articles related to human intelligence are suspect summaries often based on suspect sources, as they have been the focus of a long-standing dispute with much edit-warring
> the average IQ of the young world population would decline
I don't thinnk IQ is the right measure for that... IQ is defined in terms of the average intelligence (really, it's the median, but unless the distribution is strongly skewed, it's almost the same).
http://en.wikipedia.org/wiki/Fertility_and_intelligence
"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."[25]"
[23] http://dx.doi.org/10.1016%2Fj.intell.2007.03.002
[25] http://dx.doi.org/10.1017%2FS0021932009003344