There is a correlation between the IQ metric (whatever it represents) and income, but it's not as simple as Internet message boards want it to be: IQ reliability falls off as the scores get higher (which makes sense: IQ isn't intended as a ranking of human intelligence, but rather as a diagnostic measure for people with cognitive impairments) and income falls off as IQ scores get higher as well. Everything is complicated, as you'd expect.

First - sample sizes get smaller and smaller as you approach the edges. Law of low numbers begins to materialize.

Secondly - there’s no point in optimizing around the edge cases. As a whole it’s pretty reliable.

Everything is complicated isn’t a good reason to not take more effective action than what’s done today which is destructive and cruel. Letting stupid people, who are stupid by no fault of their own, fend for themselves and calling that liberty is why we have such poor outcomes for these people.