Various different social or racial groups in America appear to have different positions on these curves. In general.
Does that summarise it? To all except the last point, I'd say "Well, DUH!" and to the last point I'd say "Can I see your evidence and how you define a racial group? Because that seems quite unlikely." Then again, I remmeber that IQ tests are horribly flawed and very biased towards certain social norms (the language portions are especially bad) and also wonder whether it measures active intelligence, or potential intelligence. You might assume that there is a causal link between being successful and having the opportunity of good teaching etc. --Vitenka
On what grounds does it seem unlikely? Bear in mind that adult IQ is directly affected by malnutrition during pregnancy and childhood. To state that all groups in a society have an equal average IQ is to claim that all groups are equally likely to suffer malnutrition irrespective of that group's average income. --DR