IQ determine wealth and of nations

According to the recent book IQ and the Wealth of Nations, among many factors explaining why some countries are rich while others are poor, it is the people's IQ that does the heavy lifting -- for the 81 countries, the mean national IQ correlates powerfully - 0.73 - with per capita Gross Domestic Product (GDP). (In the social sciences, correlations of 0.2 are said to be "low," 0.4 are "moderate," and 0.6 are "high"; so 0.73 is most impressive).