[b] The city's annual population growth of 3.45 percent ranks as the highest among the seventy-eight largest metropolises in the Organisation for Economic Co-operation and Development.

The high population growth mirrors an urbanization trend across the country, as the second and third fastest-growing OECD metropolises are the Turkish cities of İzmir and Ankara.

[15] The remarkable growth was, and still is, largely fueled by migrants from eastern Turkey seeking employment and improved living conditions.

The vast majority of people across Turkey, and in Istanbul, are Muslim, and more specifically members of the Sunni branch of Islam.

[17] Mystic movements, like Sufism, were officially banned after the establishment of the Turkish Republic, but they still boast numerous followers.

[23] Into the 19th century, the Christians of Istanbul tended to be either Greek Orthodox, members of the Armenian Apostolic Church or Catholic Levantines.

[25] Eldem Edhem, in his entry on "Istanbul" in the Encyclopedia of the Ottoman Empire, wrote that about 50% of the residents of the city were Muslim at the turn of the 20th century.

[26] The Arabic newspaper Al Jawaib began in Ottoman Constantinople, established by Ahmad Faris al-Shidyaq a.k.a.

[29] Istanbul, the most populous city in Turkey, hosts the highest number of Syrian refugees, with approximately 550,000 registered people.

[32] Bulgarian newspapers in the late Ottoman period published in Constantinople were Makedoniya, Napredŭk or Napredǎk ("Progress"), Pravo,[33] and Turtsiya; Johann Strauss, author of "A Constitution for a Multilingual Empire," described the last one as "probably a Bulgarian version of [the French-language paper] La Turquie.

[39][40] Because of considerable presence of other non-Muslim ethnic groups like Armenians (17%), Bulgarians (3%) and the Jews (4%) at the time, Muslims were a minority in the city.

[44] The neighbourhood of Balat used to be home to a sizable Sephardi Jewish community, first formed after their expulsion from Spain in 1492.

[46][47] In large part due to emigration to Israel, the Jewish population nationwide dropped from 100,000 in 1950 to 18,000 in 2005, with the majority living in either Istanbul or İzmir.

[52][53][54][55][56][57] The Levantines, Latin Christians who settled in Galata during the Ottoman period, played a seminal role in shaping the culture and architecture of then-Constantinople during the 19th and early 20th centuries; their population in Istanbul has dwindled, but they remain in the city in small numbers.

Although the presence of Turks in Istanbul goes back to the early Ottoman times, the bulk of this population is composed of recent migrants from the Balkans and Anatolia.

[61] From the increase in mutual cooperation between Turkey and several African States like Somalia and Djibouti, several young students and workers have been migrating to Istanbul in search of better education and employment opportunities.

The largest groups of Africans that year were from Nigeria and Somalia, with the latter often working in business and the manufacturing of clothing.