I find interesting that you assume that disparity within nations is caused by differences in intelligence. While this is true (i.e.: differences in intelligence make a difference, sorry for the joke) there are many, many, other causes for differences: geographics (easy), social (not all the countries are permeable to social status changes) and so on... I feel this "all is caused by the intelligence" a bit ingenuous. But may be it is only my european culture speaking...