The World Inequality Database (WID.world) aims to provide open and convenient access to the most extensive available database on the historical evolution of the world distribution of income and wealth, both within countries and between countries.

The WID was initially created as the The World Top Incomes Database (WTID) in January 2011 with the aim of providing convenient and free access to all the existing series. The WTID expanded to include series on income inequality for more than thirty countries, spanning over most of the 20th and early 21st centuries, with over forty additional countries now under study.

Built to accompany the publishing of the two books Top Incomes: a Global Perspective (2010, Oxford University Press) and Top Incomes over the XX Century (2007, Oxford University Press). The WID offers the most comprehensive set of historical series on wealth inequality available so far.