Gabon (/ɡəˈbɒn/; French pronunciation: [ɡabɔ̃]), officially the Gabonese Republic (French: République gabonaise), is a sovereign state on the west coast of Central Africa. Located on the equator, Gabon is bordered by Equatorial Guinea to the northwest, Cameroon to the north, the Republic of the Congo on the east and south, and the Gulf of Guinea to the west. It has an area of nearly 270,000 square kilometres (100,000 sq mi) and its population is estimated at 1.5 million people. Its capital and largest city is Libreville. Since its independence from France on August 17, 1960, Gabon has had three presidents. In the early 1990s, Gabon introduced a multi-party system and a new democratic constitution that allowed for a more transparent electoral process and reformed many governmental institutions. Gabon was also a non-permanent member of the United Nations Security Council for the 2010–2011 term. Low population density, abundant petroleum, and foreign private investment[ambiguous] have helped make Gabon one of the most prosperous countries in Sub-Saharan Africa, with the 2nd highest HDI and the third highest GDP per capita (PPP) (after Equatorial Guinea and Botswana) in the region.