The NYT’s Economix blog offers a chart showing the strong correlation between parental income and SAT scores:
It is, of course, possible that this effect is entirely caused by differences in parental IQ. That said, there’s no evidence that it’s entirely caused by differences in parental IQ. But such is Greg Mankiw’s zeal to defense social and economic inequality and injustice in the United States that he slams the NYT for failing to advance this evidence-free genetic determinist theory.
But for another look at the non-genetic heritability of socioeconomic status, consider this chart Peter Orszag brought to my attention some time ago:
You see that whether or not one goes to college turns out to be closely related to parental income even when you account for differential levels of student achievement. In particular, children of average intellectual ability are likely to go to college if their parents are in the top income quartile, but not otherwise. Personally, I have no doubt that some social stratification in the United States is due to genetics, but we would have to be living in a very different country before I started using that hypothesis to wave away every potential concern about inequality.