For background reading on the topic of IQ as an objection to immigration, see IQ deficit.

I recently learned from Arnold Kling’s blog post of a new book by Richard Lynn and Tatu Vanhanen titled Intelligence: A Unifying Construct for the Social Sciences (buy here). The book is an extension of earlier work by Lynn and Vanhanen, including IQ and the Wealth of Nations (Wikipedia page).

In IQ and the Wealth of Nations Lynn and Vanhanen introduce the concept of “national IQ” — the average IQ of a nation — and then attempt to demonstrate that national IQ is correlated with a number of measures of national per capita wealth. They then try to argue that at least part of the correlation is causal from IQ to per capita wealth. Controlling for IQ, they find that the extent to which an economy is a free market economy is the best predictor of national wealth. Roughly, they contend that national IQs explain about 1/3 of the variation in national wealth, market orientation explains another 1/3 of the variation, and the remaining 1/3 is explained by a host of other factors (which they don’t attempt to enumerate in full).

In Intelligence, Lynn and Vanhanen extend the analysis beyond wealth to various other measures of well being including health measures, water access, democratization, crime, and happiness. They argue that IQ can explain a significant portion of each of these (though in some cases it is not as significant) and conventional explanations such as market orientation and specific historical events can account for some of the residual. Their overall thesis is that intelligence should be treated as a unifying construct and explanatory variable across a wide range of social sciences, akin to the way that concepts from physics have explanatory power across all domains of the natural sciences.

While L&V’s thesis is new, I think that they make reasonable arguments and attempt to address all the prima facie objections one may have. How well they succeed, and whether their thesis withstands further empirical assault, is not something I feel confident to comment upon. However, I think that L&V sometimes draw the wrong conclusions from their data on the rare occasions that they try to discuss the implications for international development.

Although I don’t have any credentials in this area, I’ve relied, in addition to L&V, on the research of Garett Jones, who largely agrees with the L&V framework but tries to dig deeper into the mechanisms by which IQ might play a causal role in creating wealth. While the synthesis I present is largely my own, it relies on Jones’ work to quite an extent.

Also note: my critique of some of the conclusions that L&V (and others) draw from their work presupposes, for simplicity’s sake, that L&V’s overall framework is correct. Even if it isn’t, and IQ is not as powerful an explanatory variable as claimed, my arguments may still work in a modified sense (replacing IQ by whatever X factor is driving national differences).

National IQs versus individual IQs

Jones, L&V, and many other students of national IQs have argued that there is a relationship between national IQ and economic measures, and that this relationship is logarithmic: a one point increase in national IQ leads to a fixed proportional increase in productivity, hence also in per capita GDP and other measures. However, one of the remarkable findings is that the effects at the national level are much more salient than the effects at the individual level. Continue reading Intelligence, international development, and immigration →