The UNU-WIDER World Income Inequality Database (WIID) presents information on income inequality for developed, developing, and transition countries. It represents the most comprehensive set of income inequality statistics available.
The fourth major edition of this database — WIID4 — was released in December 2018. Part of the 2014–2018 UNU-WIDER work programme on Transformation, Inclusion, and Sustainability, WIID4 retains several of the conceptal elements of the previous version (WIID3.4) but also incorporates many changes, both in the content and structure of the variables. This newest version also corrects for inconsistencies and other issues found in earlier editions.
With WIID4, the observations now reach the year 2017 and cover 189 countries (including historical entities), with over 11,000 data points in total. There are now almost 3,500 unique country-year observations in the database.
The WIID was initially compiled in 1997–1999, with WIID version 1.0 being published in September 2000. The WIID has long been used for research on global inequality, to analyse inequality trends across countries, as well as to study the relationship of inequality vis-à-vis (amongst others) economic growth, foreign direct investment, real exchange rates, institutional development, labour regulations, economic sanctions, public sector expansion, political conflict, religious beliefs and skilled migration.
For more, see the news item “New data on income inequality – WIID4 released” on the UNU-WIDER website.