And I thought I was being boring

My previous blog post on SAT scores and income generated a surprising amount of blogosphere pushback. See, for example, this post by Paul Krugman.

I say "surprising" because I almost did not post the piece at all, thinking that it was a bit pedantic and pedestrian. In other words, a big yawn. I did not think my point about omitted variable bias was particularly new or controversial.

In essence, what I said was

1. People vary in their innate talents, as measured by, say, IQ tests.

2. More talented people tend to earn higher incomes.

3. More talented people tend to have more talented biological children--that is, talent is partially heritable.

4. As a logical implication of the above three points, the raw correlation of kids' SAT scores and family income conflates the true effects of family income with the biological transmission of talent.

I would be curious which of the above four statements Paul does not agree with.

Paul himself is a good case illustrating my point. He is smart, and he has high income. I don't think those two facts are a mere coincidence. Instead, his innate talent is a large element of his success. I would bet that if he had had children, they would likely have been smart as well, even if he spent only average resources rearing them (such as, for example, if he put them up for adoption).

By the way, the conjecture in the final sentence of my last post about adopted kids was in part based on existing evidence in the nature-nurture debate. See, for instance, this paper.