Four, per capita incomes are also highly negatively correlated with rates of infant mortality in 1954–57 (r=−0.652), and 1999–2002 (r=−0.823). It is proposed that the principal explanation for these correlations is that populations with higher per capita incomes have higher IQs and this is the main reason why they have lower infant mortality, as argued by Gottfredson (2004).
