No surprise: Americans in the best position to have a large family are least likely to do so

A good income is associated with positive characteristics like industriousness and intelligence, traits that are strongly influenced by genes.  High-income adults are obviously in the best position to have large families.  Do they?  Look at the graph (General Social Survey, 2010-2016, women ages 40-55, household income in 1986 dollars, N = 1,325):

While women with two children have higher incomes than those with no children, income tends to fall as family size increases beyond two kids.  Compared to families with eight or more kids, two-child families earn more than double the household income.

Here's the graph for men ages 45-60 (N = 1,170):

We see a similar pattern for men, although the income drop beyond two kids is perhaps not as steep as for women. (Don't make much of the high bar for men with seven kids: it's based on only four cases.)

We're seeing the same kind of pattern again and again: Americans who are in the best position to have a big family are least likely to do so.

With these trends, the long-term future will go to the people on the bottom of American society -- the people who have the least genetic potential.