Lynn and Vanhanen
Average national IQs according to IQ and the Wealth of Nations
Average national IQs according to IQ and the Global Inequality
≤65 70 75 80 85 90 95 100 ≥105 N/A
Average national IQs according to Intelligence: A Unifying Construct for the Social Sciences (2012)
In the 2002 book IQ and the Wealth of Nations, and the 2006 book IQ and Global Inequality, Richard Lynn and Tatu Vanhanen created estimates of average IQs for 113 nations and estimated the IQs of 79 other nations based on neighboring nations and other manners. They also created an estimate of "quality of human conditions" for each nation based on gross national product per capita, adult literacy rate, the fraction of the population enrolled in secondary education, life expectancy, and rate of democratization. Lynn and Vanhanen found a substantial correlation between the national IQ scores they created and these various socioeconomic factors. They conclude that national IQ influences these measures of well-being and that national differences in IQ are heavily influenced by genetics, although they also allow for some environmental contributions. They regard nutrition as the most important environmental factor, and education a secondary factor.[6

Regarding several methodology issues of IQ and the Wealth of Nations, Hunt and Wittmann compared contemporary educational data from the Program for International Student Assessment with national wealth. They concluded that Lynn and Vanhanen's empirical conclusion is correct, but they questioned the simple explanation that national intelligence causes national wealth.[14]
In 2010, Lynn and Meisenberg integrated all the international studies of reading comprehension, math and science understanding and showed that they are perfectly correlated with national IQs. Lynn and Vanhanen's national IQ estimates were validated.[15

Hunt wrote that genetics cannot be ruled out as a possible cause, but that education surely plays a major role, so one should not conclude that human capital in poor countries can never be improved

https://www.wikiwand.com/en/Nations_and_intelligence#/Studies%20of%20national%20cognitive%20ability

Rindermann and Ceci describe the calculation of national IQs and their correlates as "a new development in the study of cognitive ability: following a century of conceptual and psychometric development in which individual and group (socioeconomic, age, and ethnic) differences were examined, researchers have turned their attention to national and international differences in cognitive competence. The goal is to use cognitive differences to understand and predict national differences in a variety of outcomes: societal development, rate of democratization, population health, productivity, gross domestic product (GDP), and wage inequality".[29

Using path analyses, Rindermann and Meisenberg have shown cognitive abilities (seen as depending on education) show a strong negative effect on HIV-infection rates, whereas gross domestic product and modernization each has a small positive effect.[39] A higher proportion of Muslims in the population reduces the HIV-infection rate.

Both genetic and environmental effects could explain national differences in IQ. It should be noted that genetic theories are not excluded by showing strong environmental effects and the environment is not excluded by assuming genetic effects.[21

Wicherts at al. conclude that this difference is likely due to sub-Saharan Africa having limited access to modern advances in education, nutrition and health care

According to Hunt, due to there being far more data available, Rindermann's analysis was more reliable than those by Lynn and Vanhanen. By measuring the relationship between educational data and social well-being over time, this study also performed a causal analysis, finding that nations investing in education lead to increased well-being later on.[20]

Hunt wrote that genetics cannot be ruled out as a possible cause, but that education surely plays a major role, so one should not conclude that human capital in poor countries can never be improved.[25]

He emphasized the environmental effect on the improvement of intelligence and wrote "overcoming the most serious environmental obstacles as deficits in health care, nutrition and education could lead in Africa within one generation to a rise of 10 to 15 IQ

Higher national education levels and IQ have a strong positive impact on democracy, rule of law and political liberty independent from GDP, according to a study by Rindermann (2008).

African countries have not yet experienced the improvements that cause the Flynn effect in the developed world, such as improvements in nutrition and health, and educational attainment.[17] Flynn also believes that the IQ gaps are fluid and will diminish greatly in the twenty-first century if no cataclysmic events happen.[60