Lynn and Vanhanan's 2002 book IQ and the Wealth of Nations, and its 2006 follow-up IQ and Global Inequality presented estimates of average IQs for 113 nations. They estimated IQs of 79 other nations based on neighboring nations or by other methods. They also created an estimate of "quality of human conditions" for each nation based on gross national product per capita, adult literacy rate, fraction of the population to enroll in secondary education, life expectancy, and rate of democratization.