Social statistics and ethnic diversity. Should we count, how should we count and why?

During the second half of the 20th century, important international migration flows have greatly contributed to the appearance of pluralist societies, and a large number of ethnic groups have emerged mainly as a result of immigration. In the context of globalization, and a slow-down of population growth in many countries, immigration and ethnic diversity represent major challenges at the dawn of the 21st century.
Among the new challenges confronting national governments, international organisations and civil society alike in the face of this growing ethnic diversity, is a rising political and social demand for evidence-based policies. This raises the question of collecting data on ethnic groups in order to estimate their number, describe their characteristics and identify factors of social and economic integration. In particular, measuring the extent and nature of the diverse forms of discrimination is essential to the formulation, monitoring and evaluation of anti-discrimination policies, be they national, regional or global.