Istanbul is Turkey's largest city by population size. In 2014, its population was approximately 14 times more than it was in 1955. This could be due to increased migration from rural areas to cities and improved healthcare. Istanbul also has the highest output per head of all regions in Turkey.
Good transport links have contributed to Istanbul's economic growth. In addition to good land transport, Istanbul is also home to the 14th largest airport in the world, measured by passenger numbers. From Istanbul, there is access to a market of $24 trillion with 1.5 billion people within a flight time of 4 hours. In addition to affordable international air travel to and from Istanbul, domestic air travel is also very affordable. This is most likely due to economies of scale. There is also a high level of competition in this industry which influences prices and quality of service. The growth in transport industries, along with growth of financial services, has contributed greatly to Istanbul's growth rate as shown in Table 1.1.