New data on income inequality – WIID4 released

The UNU-WIDER World Income Inequality Database ― widely known by its acronym WIID ― presents information on income inequality for developed, developing, and transition countries. The WIID provides the most comprehensive set of income inequality statistics available and can be downloaded here.

The new version ― WIID4 ― is the fourth major edition of the database. It is part of the 2014–18 UNU-WIDER work programme on Transformation, Inclusion, and Sustainability. WIID4 retains several elements of the concept of the previous version, WIID3.4, but it also includes many changes, both in the content and structure of the variables. This latest version also corrects for inconsistencies and other issues found in earlier editions.

With WIID4, the observations now reach the year 2017 and coverage is extended to 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 1997–99 for the UNU-WIDER-UNDP project Rising Income Inequality and Poverty Reduction: Are They Compatible? This resulted in WIID version 1.0, published in September 2000, which has been subsequently updated, expanded and developed further.

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.

Observations by variable type Number of observations
Total observations 11,101
Gini coefficients 11,054
Income distribution by quintile shares 6,933
Income distribution by decile shares 6,239


Time span Number of observations
Total observations 11,101
Before 1960 306
1960–69 670
1970–79 817
1980–89 1,381
1990–99 2,518
2000–09 3,147
2010–17 2,262


Countries included by region Number of countries
Total countries 189
Northern America 2
Latin America and the Caribbean 30
Europe 45
Middle East and North Africa 20
Sub-Saharan Africa 49
Central Asia 5
Southern Asia 9
Eastern Asia 6
South-Eastern Asia 10
Oceania 13