Six, regional IQs in 2006 are highly correlated with the years of education of adults in 1951 (r=0.929), 1971 (r=0.871) and 2001 (r=0.886). The likely explanation for these high correlations is that the populations with higher IQs keep their children at school longer. This improves the IQs of the children. The positive effect of years of education on IQ has been shown in numerous studies recently reviewed by Cliffordson and Gustafsson (2008). However, the regional differences in years of schooling amount to only about one year and it is estimated that this raises IQ by about 2.5 IQ points [...]. Hence regional differences in years of schooling do not account for much of the 14 IQ point difference between the highest and lowest IQ regions. The positive relationship between regional IQs and years of education is best envisioned as another positive feedback loop in which the population IQ is a determinant of the amount of education received by children, and the amount of education received by children is a determinant of their IQs.
