"Istanbul remains motoring power of Turkey's economy
One of the most important financial centers of the world, Istanbul continues to beat as the heart of the Turkish economy, creating 22 percent of gross national product and paying 45 percent of the country’s total taxes.
As an expanding city with population of around 13 million, according to the Turkish Statistical Institute, or TurkStat, Istanbul is the platform for more than 50 percent of total trade between Turkey and other countries."
More:Istanbul remains motoring power of Turkey's economy - Hurriyet Daily News and Economic Review