The thesis of this paper is that intelligence is a determinant of income among individuals and populations, and that national differences in intelligence are a major factor responsible for the wealth and poverty of nations. We also examine some other correlates of the IQs of nations, namely ability in mathematics and science, adult literacy, life expectancy and religious belief. Intelligence is defined as «general cognitive ability» expressed as the ability to reason, solve verbal, mathematical and spatial problems, learn quickly, remember, and acquire a large fund of knowledge (Carroll, 1993). Intelligence is measured by tests first developed in France by Alfred Binet and scored to give an IQ (Intelligence Quotient) based on a population mean of 100 and standard deviation of 15.