I'm wondering about the percentage of Christians in Asia Minor/Anatolia in the early 19th century. There were significant Muslim immigration and Christian emigration later.
Immigration: 19th century expulsion of Circassians (Muslims in religion) from Caucasus by Russians. Also, in 19th-20th century expulsion or voluntary immigration of Muslims from Balkans, after independence of Balkan states.
Emigration: Greeks in many waves, 1821, 1912-15, and their last exodus in 1922-24 after the Greek military disaster in Asia Minor and the forced relocation of reminder Greeks to state of Greece. Armenians, emigration of the reminder after the Armenian Genocide.
From what I've read most Circassians resettled in Ottoman Anatolia. The same applies for Balkan Muslims. Ecumenical Patriarchate of Constantinople's statistics, there where about 2.2 million Greeks, Christian Orthodox faith in 1912 Anatolia. There were also slaughters of Greeks and emigration to state of Greece after the Greek Revolution of 1821, which decreased their numbers. About 1 million Armenians, according to Armenian genocide numbers, were in Anatolia before the genocide, let's assume until 1900. Couldn't find much data on number of Assyrians/Syriacs of Christian faith (Oriental, Nestorian etc) probably less than a million. With a total population of about 13-14 million in Anatolia at the start of 20th century, about 3 million Christians, some thousand Hebrews, the rest Muslims, Christians were a sizable number at about 22-25% (I also expect Ottoman statistics of the era to report less Christians than their real numbers, that's why I believe Christians could be up to 25%). So before Circassian and Balkan Muslim resettlement to Anatolia and also before the first slaughter of Greeks and expulsion in 1821 from Anatolia, could Christian population in Anatolia be somewhere between 30-40% in the early 19th century?
All these numbers are debatable, gross estimations and assumptions from personal amateur reading. That's why I'm looking on scientific research on the matter. Guide me if you have knowledge of any such research.