The purpose of this project is to advance data collection, measurement, and research regarding the development of inequality in the world. A major focus in this research area is the maintenance, updating, and development of the World Income Inequality Database (WIID) which is currently the most comprehensive and complete database on inequality indicators. It gathers information on income inequality in all the countries in the world for which suitable data is available and it is freely downloadable at the UNU-WIDER website. The project also generates new research output based on WIID data. This includes a study on the drivers of within-country inequality, with a particular emphasis on the impacts of tax and spending policies. The project also contributes to the design of suitable financing of redistributive transfers systems by conducting research on tax policies in developing countries.