Istanbul, a magnet for migration both for people from other cities and abroad, attracted 416,587 more people last year, according to statistics on internal migration.
Already burdened with 15 million people, Istanbul received new residents last year from all across Turkey, according to statistics compiled by research companies Ajans Press and PRNet from TurkStat, the official statistics agency.
The capital Ankara, the second most populated city with 5.5 million people, topped the list of cities with internal migrants leaving for Istanbul. Some 17,740 people from the capital left for Istanbul in 2017, followed by Ordu, a Black Sea city in northern Turkey, with 17,452 residents leaving to pursue a new life.
The city has a population density of over 2,700 people per square kilometer and saw a construction boom, helped by a growing economy in recent years. Experts say rising demand for housing in the city that straddles Asia and Europe is here to stay at least for the near future as Istanbul is still the main financial hub of the country and offers vast business opportunities for millions.
Statistics also looked into cities where the least migrants came from last year. Only 593 people arrived in Istanbul from Karaman, a small city in the Anatolian heartland followed by Kilis along the Syrian border.
A reverse migration program launched 21 years ago by then Istanbul Mayor Recep Tayyip Erdoğan has seen more than 157,000 people return to their hometowns from Istanbul. The municipality's initiative covers transportation fees for families or free bus tickets. The program, initially overseen by municipal police, is now being carried out in coordination with social services and mainly targets impoverished families. Families need to document their financial status to be granted migration incentives. In the past four years, more than 13,083 families have left Istanbul for their hometowns due to the program. Along with families who sought to set up a new life in the city but failed to prosper, the program covers students and patients who undergo treatment in Istanbul but cannot afford to travel back to their hometowns.