In April 2016, South Korea's population was estimated to be around 50.8 million by National Statistical Office, with continuing decline of working age population and total fertility rate. The country is noted for its population density, which was an estimated 505 per square kilometer in 2015, more than 10 times the global average. Aside from micro-states and city-states, South Korea is the world's third most densely-populated country. In practice the population density in much of South Korea is higher than the national one, as most of the country's land is uninhabitable due to being used for other purposes such as farming. Most South Koreans live in urban areas, because of rapid migration from the countryside during the country's quick economic expansion in the 1970s, 1980s and 1990s. The capital city of Seoul is also the country's largest city and chief industrial center. According to the 2005 census, Seoul had a population of  inhabitants. The Seoul National Capital Area has  inhabitants (about half of South Korea's entire population) making it the world's second largest metropolitan area. Other major cities include Busan (), Incheon (), Daegu (), Daejeon (), Gwangju () and Ulsan ().