U.S. Household Income v. Children Per Woman Per Lifetime (TFR)

From here.

Women from households with low income and very high incomes have the most children per lifetime, while middle and upper middle income women have the fewest children per lifetime.

In pre-modern history, everyone had more kids, but everyone had lots of children who died young.

Affluent women have fewer children, to a significant extent, because they postpone marriage and child bearing to gain more higher education and to establish professional careers after doing so. Women who don't pursue as much higher education or as high end careers don't wait as long (and often have children first, and marry second, if they marry at all).

Women on track to be highly educated, professional women with highly economically successful careers pay a very high economic prices for doing so that extends long after they return to the work force. In contrast, women whose market economic activity involves jobs that require little education pay a quite low and rarely extends a long time after they return to the work force.

Affluent women have children at a much greater age, on average, something that fertility treatments help to facilitate. The "trophy wife" phenomena of affluent men marrying much younger women (sometimes in second marriages) is also a factor.

Only women with household incomes of less than $25,000 a year and more than $1,000,000 a year have children at or in excess of the replacement rate of 2.1. Women in households with incomes of less than $25,000 a year are in less than the bottom 10% of income. Women in households with incomes of $1,000,000 a year are in the top less than 1% of income. About 95% of women have household incomes associated with a less than a 2.1 replacement rate TFR.

Lower income women having more children are much more numerous than higher income women having more children, as illustrated by this graph:

Race is also factor in TFR although not a huge one (a factor somewhat diluted by the chart below which lumps all non-white categories together). 

Religion would be a better distinguishing factor (with Mormons, Hispanic Catholics, and Evangelical Christians having higher TFRs), but isn't present from this source because the American Community Survey (a research project of the Census Bureau in the U.S. Commerce Department) doesn't ask about religion to avoid church v. state issues, so the relationship has to be inferred from other data.

The TFR of lower income women has fallen considerably in recent years, while the TFR of women in high income households has grown in the same time period.

But, the small magnitude of the impact of household income on TFR is also notable. There is a variance of less than 0.5 children per lifetime in TFR in the entire household income range of $50,000 per year to $499,999 per year. The TFR of households with incomes of $1,000,000 per year or more is a mere 2.4 or so and the lowest income women have a TFR of only a little more than 2.1. The magnitude of the income effect on TFR is even smaller for white women.

Economic success is negatively correlated with reproductive fitness up to $199,999 per year of household income. Economic success is far less than linearly correlated with reproductive fitness at household incomes of $200,000 per year and more. 

Even billionaires don't have that many kids per lifetime, in stark contrast to per modern times, and this isn't just due to men having a small number of mates. Women in high income households also don't have nearly as many children as they could without any economic strain.

This chart also suggest the possibility that higher TFR in rural than in urban areas may be related to lower income in rural than in urban areas.

It also demonstrates that eugenics is not a very powerful ideology in U.S. politics.