In his contribution to the "What Is Inequality?" series, Pedro Ramos Pinto provides a critical history of both scholarly and public attention to inequality. Ramos Pinto examines the development of GDP as a mode of comparing inequality across nation-states as well as recent efforts at documenting changes in income distribution within countries. He concludes with a paradox: a principal focus on the income levels of individuals risks oversimplifying and misunderstanding inequality, but at the same time provides a concise and potent rallying cry for egalitarian movements that contest it.