The nature of the relationship between economic development and income inequality has long been the subject of considerable debate. Economic growth has very different effects on poverty, depending on a country’s level of income inequality. In high inequality countries, economic growth that raises the overall level of income disproportionately tends to benefit the rich, whereas policies that encourage economic growth while reducing income inequality will greatly accelerate the achievement of poverty reduction goals. Thus, understanding how income inequality and economic development are linked is important for establishing economic growth policies that reduce poverty. The literature on the economic development–income inequality nexus in industrial society places emphasis on the causes of current social inequality. The central and most cited paper in the literature is S. Kuznets’s “Economic Growth and Income Inequality” (1955), which proposed an inverted U-shaped relationship between development and inequality over the course of industrialization. Some scholars have tried to build upon Kuznets’s theory by focusing on his claim that income inequality is a function of the nature of regulations put on the market. Other studies deal with the importance of studying the relationship between democracy and inequality, the effect of the nature of the government on shaping inequality compared to industrialization, and the implications of globalization for income inequality. This overview of the literature shows that there is little true consensus on the relationship between inequality and development and highlights two major areas for improvement: measurement and data quality.