I'm surprised to find no mention of SES or income in the article. There can be similar Simpson's paradox effects within racial groups between states (for instan

I'm surprised to find no mention of SES or income in the article. There can be similar Simpson's paradox effects within racial groups between states (for instance, Iowa might have more low SES white people than Texas). I would have expected this to be mentioned in the article for why they chose not to account for it in some form.