It's a U-curve as well. Very poor people have low standards when it comes to raising children and less qualms about raising families on welfare with limited opportunities. Once people become educated and middle class but still poor, they have higher aspirations for their children and are less prone to have children if they know they won't be able to provide an adequate standard of living. Rich people have typically an above average number of children. I was mostly talking about the middle class, the ones who are educated but still poor.