What has been documented in books such as The Bell Curve is that IQ and socioeconomic status is positively correlated, and that IQ somewhat heritable, which explains the empirical finding that a higher fraction of rich kids than poor kids are gifted.
But when you take a look at Murry
http://www.aei.org/docLib/20040302_book443.pdf at the begining of chapter 2, he says that he broke his groups down into 5 classes at the 10th,25th,75th,and 90th percentile.
So as far as I know, there is no data looking at income in Optimally Gifted, Highly Gifted and Profoundly Gifted catagories, no matter what definition one gives them. The majority of kids in the 'over 90th percentile' catagory can be expected to get a decent-fit education without their parents doing much of anything.
So I would suggest from personal experience that HGs and PGs vary all over the map on many personal characteristics, including income.
I heard about something in medicine once called the Starling Curve, and the expression 'falling off the Starling Curve'
http://en.wikipedia.org/wiki/Cardiac_function_curveand I've often thought that a lot of natural phenomenon must mimic this. One can be under pressure and rise to the occasion to a degree, quite sharply at first in fact, and then with increased stress, the gains get smaller and smaller, perhaps even being lost. My hunch is that the income/IQ curve is quite linear throughout most of the trip, but resembles more of a Starling Curve as one gets up in the HG/PG zone. Afterall, if the income curve was perfectly linear, and at least 2/3rd of HG/PG kids came from HP/PG parents, there wouldn't be much discussion about how to negotiate with schools, and more about how to find the best private tutor, yes?
Or do I have more straw between my teeth?
Grimity
