[tptacek]

You understand that the perception that you're looking at someone's skin color or facial features, making a prediction as to whether they ingested lead paint as a child, and then acting accordingly is going to be problematic, right?

[0815test]

But of course no one sane is doing anything of the sort. The issue is how to explain the difference between "% of people with visible feature X in the general population" and "% of folks with feature X who happen to be math PhD's". Well, if feature X correlates with issues like eating lead paint as a kid, even to a small, otherwise undetectable extent, you're going to find that sort of difference.