At a higher level of generality, positive correlations between IQ and per capita income have been reported for populations in geographical regions within countries. Studies reporting this have been published for the British Isles, France, and the United States. The first of these studies was concerned with IQ differences in 13 regions of the British Isles in the mid-twentieth century [...]. It was found that the highest IQ (102.1) was in London, and the lowest IQs in Scotland (97.3), Northern Ireland (96.7), and the Republic of Ireland (96.0). These regional IQs were positively correlated with per capita income at 0.73. They were also positively correlated with intellectual achievement indexed by fellowship of the Royal Society (r=0.94), and negatively with infant mortality (r=−0.78) [...]. It has been shown subsequently that these regional differences in IQ are strongly associated negatively with differences in stature [...].
Similar results have been found in France, where regional differences in intelligence were reported for the mid-1950s by Montmollin (1958). IQs were obtained from 257,000 18 year old male conscripts into the armed forces, and mean IQs were given for the 90 French departments.
The highest IQs were obtained by conscripts from the Paris region and the lowest by conscripts from Corsica. As in the British Isles, it was shown that these departmental IQs were moderately well positively correlated with average earnings (r=0.61), with intellectual achievement indexed by membership of the Institut de France (r=0.26), and negatively with infant mortality (r=0.30) [...].
An association between regional IQ and per capita income has also been reported in the United States. It has long been known that in the United States the populations of the northern states have higher average IQs than those of the south east [...]. This has been confirmed by McDaniel [...] who has calculated the IQs of the populations of the American states and found that these are highest in the north eastern states of Massachusetts (104.3), New Hampshire (104.2) and Vermont (103.8), and lowest in the southern states of Mississippi (94.2) and Alabama (95.7), and in California (95.5). The McDaniel [...] average state IQs are positively correlated with gross state product per capita (a measure of per capita income) at Pearson's r=0.28. These state differences in average IQ are partly determined by the proportions of blacks and Hispanics, who have lower average IQs than Europeans at approximately 85, 89, and 100, respectively [...]. McDaniel [...] calculated that state IQs are correlated at −0.51 with the percentage of blacks and −0.34 with the percentage of Hispanics. Similar state differences in IQ using a different methodology have been reported by Kanazawa (2006). The different methodologies are discussed by McDaniel [...].
