Mark Regnerus reports some early results of his survey of young adults, 18 - 39.
I was drawn to this portrait of the number of children in each family. These data are on full brothers and sisters.
Only children: 21%
Two-child family: 34%
Three-child family: 24%
Four-child family: < 10%
Five-child family: < 5%
Thus, most families don't have enough children to replace the population (replacement level is, on average, 2.1 children per woman). When you consider the people in the parental generation (older than these respondents) who had no children, they balance out those who had four or more kids. The average educated mother has two children, which is a widely known norm. What is less well known is that poor, unschooled, teen mothers also have, on average, two children.
Sociologists have known for some time that the population of this country is in danger of declining, as it is likely to do in all other industrialized countries. Many of my students feel freed by this news, as they want to have more than two children but were afraid that was irresponsible. They had been taught the old story of a "population explosion" that their parents were taught. The idea that they can have more is liberating.
The threshold for a stable population, I believe, is between two children as a norm, and three. People like my students are the very kind most likely to be able to create stable families - educated, persistent young people who are no longer teenagers.
America would be better off if the norm for stable families was three children, rather than two.
As I have long urged my students, when thinking about family size, consider three.