I've been doing a little work with regard to the Treaty of Sèvres (particularly as regards "Wilsonian" Armenia) and as part of that I've been plotting out the demographic/ethnographic population figures used by the American Commission to Negotiate Peace. These were used to help evaluate and define the boundaries of new entities to be created by the treaty, namely "Wilsonian" Armenia, Kurdistan, the Republic of Pontus and the Smyrna Zone among others.
As the Ottoman Census, as well as provincial almanacs were known - even then - to be notoriously inaccurate (women in general were undercounted, and Christian populations were also systemically undercounted - namely due to deliberate obfuscation by Christian authorities/communities themselves, deliberate omission by Ottoman authorities, and a lack of government authority on the ground as local Kurdish chiefs treated Christians as more-or-less their cattle). So the Americans, who were given total authority to determine Armenia's boundaries, had to rely on other figures including Cuinet Vital's figures and statistics reported by Christian clergy & American residents of Anatolia.
These figures were collated, synthesised and corrected as best as possible by Prof. David Magie in Inquiry Document 1005, The Population of Asiatic Turkey at the Outbreak of the War
. These population estimates, which (unlike Cuinet Vital) are carefully and systematically explained, formed what were probably the best & most well-educated estimates available to the great powers at Sèvres. It was The Population of Asiatic Turkey at the Outbreak of the War
, which in Woodrow Wilson's Arbitral Award of the President of the United States of America
is only referred to as "report upon the "Population of Asiatic Turkey"" which was used as a major point of reference in drawing up "Wilsonian" Armenia's boundaries, as well as was used to reject similar proposals including the erstwhile Republic of Pontus.
The population is presented as per Sanjak of Ottoman Anatolia, as well as the Levant and Mesopotamia (though it is only Anatolia I'm interested in). Of these, only in Smyrna Sanjak (Aydin Vilayet) do Greeks predominate over Muslims, and only in Mush & Van Sanjaks that Armenians predominate over Muslims.
In most instances, Magie was unable to separate different Muslim populations from each other: The only exceptions are in Maramuret-ul-Aziz Vilayet, where "Turks" are given as separate from "Kurds and Qizilbash" (Qizilbash being Shi'a Turkomans), and in Van Vilayet were "Turks" are given separate from "Kurds". In all other cases, it was not realistically feasible to give ethnic identifiers to Muslims per Sanjak, although in some cases The Population of Asiatic Turkey at the Outbreak of the War
does give convincing estimates for the Vilayet as a whole:
1) Bitlis Vilayet: Of “Turks and Kurds”, there were 60,000 Turks and 201,000 Kurds (incl. nomads) of the entire vilayet.
2) Diyarbekir Vilayet: Of “Turks, Kurds, Arabs” there were respectively 100,000, 230,000 and 70,000 of the entire vilayet.
3) Erzurum Vilayet: Of “Turks, Lazes, Kurds” there were respectively 335,000, 29,000 and 176,000 of the entire vilayet.
Basically, unless I'm much mistaken, these were the most accurate demographic records of the Ottoman Empire available at the time of its dissolution - though still, of course, flawed. If I get the time I'll map out the rest of the Ottoman Empire in Asia from the same records.
(Edit: Basemap used is one from Histatlas, from "Middle East" folder.