Earl B. Hunt writes that economists traditionally view differences in wealth between nations in terms of human capital, which is a general term for the abilities of the workforce. However, some researchers have argued that differences in average intelligence between nations also play a role. Richard Lynn and Tatu Vanhanen published the books IQ and the Wealth of Nations and IQ and Global Inequality, which led to further investigations from other researchers, some of them highly critical of Lynn and Vanhanen's methods and conclusions.[1]