The Ottoman Empire population consisted of diverse peoples. Not much is known about the first half of the Ottoman Empire because proper records were not maintained. But it is known that the Ottomans had a variety of people within the boundaries of their Empire. This is probably why there was such a rich intermingling of culture and exchange of ideas in the region.
But in the latter half, their population was recorded, probably due to influence of the Western forces. Before World War I, in 1914, the total population of the Ottoman Empire was about twenty five million. Ten million of this total consisted of Turks, six million consisted of Arabs, one to two million were Armenians, One and a half million Greeks and one and a half million Kurds. This shows that quite a diverse people comprised the Ottoman Empire population.
But for the first half of the Empire, not too many records except the numbers of working members among the population. Old data was used until 1881-1883, when the first census was carried out. This data was used to extend taxation values to the population.
However, this data was very accurate, for Ottoman cities, towns or settlements which had larger than five thousand people. This is because this data was collaborated with data about wages and prices.
Another way to find out the Ottoman Empire population arises from the number of households. On an average, every household in the Ottoman Empire was thought to have about five surviving offspring and this was used as a basis for calculation.
The first official census to determine the Ottoman Empire population took about ten years to finish. There was no specific purpose for carrying out this census. It was in fact, the first modern census, done exclusively to calculate the Ottoman Empire Population. It was done in a systematic manner and the population was divided into various ethno religious categories, as well as those of gender.
After this first census in 1893, the Ottoman Empire established an authority to exclusively conduct this census called the Istatistik-i Umumi Idaresi. They carried out an extensive survey, a lot of which was not published. However, their substantial work has been used as a basis for many a modern study,
But the Ottoman Empire population was drastically lowered in the period before the World War due to several battles and general unrest, however, it continued to remain diverse and culturally rich.