Poverty and inequality have pervaded British society to this day, but this has not always been self-evident to contemporaries – popular understandings have depended on existing knowledge. Inequality Knowledge provides the first detailed history of the numbers about the gap between rich and poor. It shows how they were produced, used, and suppressed at times, and how activists, scientists, and journalists eventually wrestled control over the figures from the state. The book traces the making and the politics of statistical knowledge about economic inequality in the United Kingdom from the post-war era to the 1990s. What kind of knowledge was available to contemporaries about socio-economic disparities in Britain and how they evolved over time? How was this knowledge produced and by whom? What did policy makers and civil servants know about the extent of poverty and inequality in British society and to what extent did they take the distributional impact of their social and fiscal policies into account? Far from just a technical matter, inequality knowledge had far-reaching implications for key debates and the wider political culture in contemporary Britain. Historicizing inequality knowledge speaks to a long tradition of historical research about social class divisions and cultural representations of economic disparities in twentieth-century Britain.