The population of Finland is currently about 5.5 million. The current birth rate is 10.42 per 1,000 residents, for a fertility rate of 1.49 children born per woman, one of the lowest in the world, significantly below the replacement rate of 2.1. In 1887 Finland recorded its highest rate, 5.17 children born per woman. Finland has one of the oldest populations in the world, with a median age of 42.6 years. Approximately half of voters are estimated to be over 50 years old. Finland has an average population density of 18 inhabitants per square kilometre. This is the third-lowest population density of any European country, behind those of Norway and Iceland, and the lowest population density of any European Union member country. Finland's population has always been concentrated in the southern parts of the country, a phenomenon that became even more pronounced during 20th-century urbanisation. Two of the three largest cities in Finland are situated in the Greater Helsinki metropolitan area—Helsinki and Espoo,  and some municipalities in the metropolitan area have also shown clear growth of population year after year, the most notable being Järvenpää, Nurmijärvi, Kirkkonummi, Kerava and Sipoo. In the largest cities of Finland, Tampere holds the third place after Helsinki and Espoo while also Helsinki-neighbouring Vantaa is the fourth. Other cities with population over 100,000 are Turku, Oulu, Jyväskylä, Kuopio, and Lahti. On the other hand, Sottunga of the Åland Islands is the smallest municipality in Finland in terms of population (Luhanka in mainland Finland), and Savukoski of Lapland is sparsely populated in terms of population density.