A numerical estimate of the scope of contemporary diasporas is essential for any further analysis of the phenomenon. However, as in the case of the data pertaining to other aspects of contemporary ethnicity, it is extremely difficult to obtain anything approaching precise figures on the actual sizes, compositions, and dispersals of ethno-national diasporas. The lack of accurate data and the ambiguity in the available statistics are connected to what can be called the “data politics” of the diaspora phenomenon. Moreover, that illustrates the great social and political sensitivity of this issue for all parties involved – homelands, host governments, other ethnic groups residing in host countries, and the diasporic entities themselves. In other words, to some extent the unavailability and inaccuracy of such data are neither accidental nor the result of “objective” difficulties in data collection and processing. In most cases the problem stems from deliberate policies of homelands and host governments intended to suppress or falsify information about modern diasporism, that is, to conceal its actual impressive magnitude, rapid growth, and emerging significance.

The European Union provides a good illustration of such data politics. It is true that information about place of birth and citizenship is available from most European Union member states. Some European Union countries, however, prohibit the registration of ethnic origins, culture, race, religion, and political affiliation of migrants. That is a new development. Before and during World War II such registration was the norm in most of the European states.