I think the OP has the arrow of causation pointing the other way from what you suggest: that is to say that higher intelligence leads to higher SES because know

I think the OP has the arrow of causation pointing the other way from what you suggest: that is to say that higher intelligence leads to higher SES because knowledge work tends to be higher SES and those with higher intelligence are more likely to be able to find employment in knowledge work professions. That is probably predicated on the existence of at least some social mobility though.