Richer People Didn't Always Have Fewer Children

It's generally taken as a given in contemporary political debates -- and sometimes expressed not all that tactfully -- that there's a negative correlation between economic well-being and fertility. People in rich countries, and richer people within countries, tend to have fewer kids.

But a statistical analysis by Princeton University's Tom Vogl, published by the National Bureau of Economic Research, suggests this correlation is relatively recent in much of the world. Vogl used fertility data to create "cross-sections of families from 20 countries in the 1986-1994 and 2006-2011 periods." Here's what he found:

"Between these periods, the relationship between parental economic status (measured by durable goods ownership) and the number of surviving children flipped from positive to negative in the African countries in my sample, as well as in the rural parts of Asia in my sample. The relationship was negative throughout in Latin America, leading one to wonder whether these data capture the tail end of a global transition.…

A wide range of data from 48 developing countries reveals that both associations were indeed positive well into the 20th century. They became negative only recently: first in Latin America, then in Asia, and finally in Africa.

Vogl also finds that in his sample, "increases in the parent generation's education were by far the most important predictor of the reversal," as opposed to more commonly cited factors like GDP, child mortality, urbanization, and women's labor force participation, countering the stereotype that poor families have more children because they're needed for farm labor or because it's assumed that some won't make it to adulthood.

This is interesting to consider in light of other research making the case that gains in "effective labor supply"-- healthier, more educated people -- can make up for losses in productivity as fertility rates fall in wealthier countries.

BEHROUZ MEHRI/AFP/Getty Images