The Lauren Bacall comment is true. DW was president/ceo for a few years and now has taken a less visible job and has turned down promotions. She decided to focus on the family for a while. I've done the same thing - scaled back my work hours to under 60 and pushed more work onto subordinates and hired a few more people.
DW and I would like a 3rd and perhaps a 4th kid, but some complications from #2 have precluded that.
Empirical research shows that number of kids is tied to political beliefs and marginal tax rates. More conservative people have more kids and lower marginal rates are associated with more kids. So I am not so sure that IQ selects for fewer kids. (US tax rates are still indexed to income and there is a huge marriage penalty.)
http://mjperry.blogspot.com/2007/04/employment-gaps-fertility-rates-and-tax.htmlhttp://www.jasoncollins.org/2011/05/the-heritability-of-feminism/Also, income also correlates with age. Younger people tend to want more kids and older people, less. Income rises with age. I think you would have to go back and look at the final net worth.
Finally, if we assume IQ is dominant genetically, then higher IQ will spread quickly throughout a population, even if couples self-select for dominant traits.
