Samoa is a unitary parliamentary democracy with eleven administrative divisions. The sovereign state is a member of the Commonwealth of Nations. Western Samoa was admitted to the United Nations on 15 December 1976. Because of the Samoans' seafaring skills, pre-20th-century European explorers referred to the entire island group (which includes American Samoa) as the "Navigator Islands.” The country was a colony of the German Empire from 1899 to 1915, then came under a joint British and New Zealand colonial administration until 1 January 1962, when it became independent.