Michelle Budig, in a new paper,http://www.thirdway.org/publications/853, cf also
http://www.nytimes.com/2014/09/07/upshot/a-child-helps-your-career-if-youre-a-man.html?_r=0&abt=0002&abg=1
regressed data in National Longitudinal Survey of Youth from 1979 to 2006 and claims that guys who had a kid they lived with had earnings increase 6%, while women’s decreased 4% for each child they had.

Naturally, she interprets this as implying discrimination against women. But I regard it as pretty good news for the future. If women’s earnings decrease 4%, that likely mostly shows that women are choosing to invest in their children rather than focus on their jobs.
If men’s earnings are actually increasing by 6%, that doesn’t seem likely to be because their employers think:
“this guy’s joined the Old Boys Network, I should give him a raise” just at the time when a lot of guys do lose sleep and devote time to child raising that might have been devoted to their job and have a new dependent to weigh further on the company’s health care premiums. I think its much more likely showing that women choose to have kids with guys who are going somewhere, not losers, and guys choose to have kids when they think they will be able to support them (and have a woman who thinks they are worthy). (But I’d like to see the data on men who had kids they didn’t live with.)

This sounds like good news for the IQ of the population. Income is presumably a reasonable proxy for IQ, since IQ is supposed to be about an ability useful for solving general problems, and earning money is a particular example of a general problem people are motivated to solve. If IQ means much, any problem people are motivated to solve that involves intelligence is something of a proxy for IQ, and they all should give similar results.

It is sometimes said that the population IQ must be decreasing, because poorer, and hence on average lower IQ women are said to have more children than wealthier and on average smarter ones. I’ve seen this claim from liberal Princeton Bio-ethics professors (Silver in a public lecture) to reactionary British ones https://archive.org/details/Dysgenics-Richard-Lynn and widely on the man-o-sphere (cf comments at http://blog.jim.com/science/dysgenic-fertility/ http://heartiste.wordpress.com/2014/08/01/is-the-collapse-of-america-inevitable/ ) I’ve long critiqued it because it discounts men, and sexual selection, which I have long believed to be possibly the primary force in the evolution of human language, among other things.

But in this study, men’s incomes increased more than women’s decreased, and both were likely weighed upon further by lifestyle/child investment decisions and the actual costs imposed by child raising on the employer, so that the income proxy probably systematically under-estimates the correlation between higher IQ and more children. This suggests that the amount that mean paternal IQ is higher than mean IQ much more than compensates for the amount that mean maternal IQ may (or may not) be lower than mean IQ.