[Earlier by J. Philippe Rushton: Winters Are Good For Your Genes…]

IQ and Global Inequality, the new book by Richard Lynn and Tatu Vanhanen, is an elaboration and extension of their IQ and the Wealth of Nations, which was reviewed on VDARE.COM by myself and by Steve Sailer. In that book the authors presented measured IQs for 81 countries and estimated IQs for the remaining countries in the world—a total of 185. They showed that these IQs correlated around 0.70 with per capita income and rates of economic development. This was predictable, they argued, because intelligence is correlated with earnings among individuals. Nations are aggregates of individuals, so the same correlation could plausibly be expected across nations.

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. The problem has also been addressed by sociologists, historians, psychologists and most recently by an evolutionary biologist, Jared Diamond. None of these have suggested that national differences in intelligence might be a major factor determining why some nations are so rich while others are so poor.

Perhaps they lacked the courage.

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. For instance, Richard Easterlin, then Kenan Professor of Economics at the University of Pennsylvania, wrote in 1981:

"I think we can safely dismiss the view that the failure of modern technological knowledge to spread rapidly was due to significant differences among nations in the native intelligence of their populations." [Why Isn't the Whole World Developed? Journal of Economic History, Vol. 41, No. 1]

As another, more recent example, we meet the same claim in December 2000 by Eric Hanushek and Dennis Kimko in The American Economic Review:

"We assume that the international level of average ability of students does not vary across countries" [Schooling, Labor-Force Quality, and the Growth of Nations (PDF)]

This assumption that the average level of intelligence is the same in all nations is seriously wrong. Lynn and Vanhanen have found huge national differences in average 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. This is very significant.

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").

Lynn and Vanhanen's work got a mixed reception. Some were convinced; others were vehemently hostile. Many preferred to ignore the idea.

In IQ and Global Inequality, Lynn and Vanhanen build on their previous work and extend it in six directions.

• First, they 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.

• Second, they use the same method for estimating the IQs of countries for which they were unable to provide measured IQs, i.e. from neighbouring countries with culturally and racially similar populations (e.g., the IQ of Latvia is estimated at 98 from the measured IQs of 99 in Estonia and 97 in Russia). By the use of this method, they provide IQs for all 192 countries in the world. For these the correlation between IQ and per capita income for 2002 is 0.60.

• Third, they address the argument made by several critics of the invalidity of the estimates of national IQs from the measured IQs of neighbouring countries. They show that there is a correlation of 0.91 between the estimated IQs for 32 countries given in their first book and the measured IQs for the same countries given in their new book. This establishes their case that the estimated IQs were remarkably accurate.

• Fourth, a number of critics attacked the reliability and validity of the national IQs. To address this question the new book presents results of 71 countries for which two independent measures of IQ have been obtained and show that the correlation between these is 0.95, which is a very high reliability. To establish the validity of national IQs they present the results of national scores from tests of mathematics and science. These correlate with national IQs from 0.79 to 0.89, which is a very high validity.

• Fifth, IQ and Global Inequality examines the relation between national IQs and a variety of social phenomena. 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 democratization (0.57).

  Of course, some of these phenomena have positive feedback relationships. For instance, countries 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.

• Sixth, 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 countries (China, Japan, South Korea, Taiwan, Hong Kong and Singapore) all have IQs in the range of 105 to 108. The 29 European countries all have IQs in the range of 92 to 102. The 19 countries of sub-Saharan Africa all have IQs in the range of 59 to 73. Thus there is remarkable consistency in the IQs of countries when these are classified into racial clusters.

As often happens with important discoveries in science, the fact that these national differences in intelligence must inevitably determine differences in economic development seems obvious in retrospect.

Indeed, it seems astonishing that no-one had hitherto advanced this simple thesis—even before the recent Dark Age of Political Correctness closed in.

J. Philippe Rushton [email him] is a professor of psychology at the University of Western Ontario, the author of Race, Evolution, and Behavior: A Life History Perspective.