IQ and Global Inequality
This new book by Richard Lynn and Tatu Vanhanen is an elaboration and extension of their IQ and the Wealth of Nations (2002) in which they showed that IQ scores correlated around 0.70 with per capita income and rates of economic development in over 81 countries.  This was a very bold claim. The cause of national differences in wealth is one of the major problems in economics. Hundreds of books have been written on the subject and several journals are devoted to it. Only very rarely is it ever suggested that national differences in intelligence help determine why some nations are so rich while others are so poor.  In my view, Lynn and Vanhanen have made what is arguably the most important contribution to economic understanding since Adam Smith showed that free markets promote economic development.  They have shown also that national IQs explain much of the variation between nations in a wide range of economic and social phenomena--not just income levels.  Their book extends the explanatory power of the concept of intelligence in a way that makes a major contribution to the integration of psychology with the other social sciences.  In advancing their intelligence theory, Lynn and Vanhanen begin by noting that economists usually regard it as axiomatic that all peoples of the world have the same intelligence.  The assumption that the average level of intelligence is the same in all nations is seriously wrong. Lynn and Vanhanen have examined the matter. They found huge national differences in intelligence. Some countries in sub-Saharan Africa appear to have average IQs of 67. Some of the "Asian Tiger" nations of the Pacific Rim average out at 105.  For perspective, the reader might note that an IQ of 70 is the lower limit for primary school educability, and an IQ of 105 the lower limit for College-level (although of course these can always be "dumbed down."  In IQ & Global Inequality, Lynn and Vanhanen have increased the number of countries for which they have calculated measured IQs from 81 to 113. They show that in the new larger sample of 113 countries the correlation between IQ and per capita income for 2002 is 0.68, virtually identical to the correlation reported in their earlier book.  A path model in which genes and environment both contribute equally (0.50) to national IQs allows a determination of economic growth (0.71) from 1500 to 2000. These national differences in the rate of economic growth are almost entirely responsible for the contemporary differences in per capita income (0.98). The model also posits that national IQs are determinants of a number of social phenomena such as adult literacy (0.64), enrolment in tertiary education (0.75), life expectancy (0.77), and democratisation (0.57).  Some of these phenomena have positive feedback relationships. For instance, nations whose populations have high IQs have high per capita incomes, which enable them to provide high quality nutrition, education, and health care for their children, and these enhance their children's intelligence. This is the principle of genotype-environment correlation applied to national populations.  IQ & Global Inequality addresses more fundamentally the question of the causes of national differences in intelligence. It concludes that these depend on the racial composition of the populations. Thus, the 6 East Asian nations (China, Japan, South Korea, Taiwan, Hong Kong and Singapore) all have IQs in the range of 105 to 108. The 29 European nations all have IQs in the range of 92 to 102, while the 19 nations of sub-Saharan Africa all have IQs in the range of 59 to 73. Thus there is remarkable consistency in the IQs of nations when these are classified into racial clusters.  Like many important discoveries in science, it seems obvious in retrospect that these national differences in intelligence must inevitably --J. Philippe Rushton