There is a Muslim minority who are Greek citizens living in Thrace, concentrated in the Rhodope and Xanthi regional units. According to the 1991 census, there were 98,000 Muslims in western Thrace, 50% of them of Turkish ethnic origin, with 35% Pomaks and the remaining 15% Roma. Other sources estimate the size of the Muslim minority at 0.95% of the population, or approximately 110,000. Aside from the indigenous Muslim minority in Greece, the Muslim immigrant population in the rest of the country was estimated at 200,000 to 300,000, though these are recent migrants and generally not considered a minority. Under Greek administration, the Muslim minority of Greece has adopted a moderate, non-political form of Islam. The Lausanne Treaty and as a result the Greek government define the rights of the Muslim communities in Western Thrace, both Turkish and Pomak, on the basis of religion instead of ethnicity.