Cape Verde /ˌkeɪp ˈvɜrd/ (Portuguese: Cabo Verde, pronounced: [ˈkabu ˈveɾdɨ]), officially the Republic of Cabo Verde, is an island country spanning an archipelago of 10 volcanic islands in the central Atlantic Ocean. Located 570 kilometres (350 miles) off the coast of Western Africa, the islands cover a combined area of slightly over 4,000 square kilometres (1,500 sq mi). Three (Sal, Boa Vista and Maio) are fairly flat, sandy and dry; the others generally rockier with more vegetation.Historically, the name "Cape Verde" has been used in English for the archipelago and, since independence, for the country. In 2013, the Cape Verdean government determined that the Portuguese designation "Cabo Verde" would henceforth be used for official purposes, such as at the United Nations, even in English contexts. Portuguese explorers discovered and colonized the previously uninhabited islands in the 15th century. Ideally located for the Atlantic slave trade, they grew prosperous and often attracted privateers and pirates, among them Sir Francis Drake, a corsair privateering under Letter of marque granted by the English crown who twice sacked the (then) capital Ribeira Grande in the 1580s. The islands were also visited by Charles Darwin's expedition in 1832.Decline in the slave trade in the 19th century resulted in an economic crisis. With few natural resources and inadequate sustainable investment from the Portuguese, the citizens grew increasingly discontented with the colonial masters, who nevertheless refused to provide the local authorities with more autonomy. A budding independence movement (originally led by Amílcar Cabral, assassinated on 20 January 1973) passed on to his half-brother Luís Cabral and culminated in independence for the archipelago in 1975.Cape Verde's population is mostly creole; its capital city Praia accounts for a quarter of the country's estimated 500,000 citizens. Over 65% of the population in the archipelago lives in urban centers, and the literacy rate is around 87% (i.e., 91% among men aged 15 above and 83% among women aged 15 above) according to the 2013 Cape Verdean census. Politically, the country is a very stable democracy. Its notable economic growth and improvement in living conditions despite a lack of natural resources has garnered international recognition, with other countries and international organizations often providing development aid. Since 2007, Cape Verde has been classified as a developing nation.Tough economic times during the last decades of its colonization and the first years of independence led many Cape Verdeans to emigrate to Europe, the Americas and other African countries. Today these émigrés and their descendants outnumber the domestic population. Historically, remittances from these émigrés to their extended families in Cape Verde has provided a substantial contribution to the country's economy. However, later generations are less likely to send money back and currently, the Cape Verdean economy is mostly service-oriented with a growing focus on tourism and foreign investment, which benefits from the islands' warm year-round climate, diverse landscape and cultural wealth, especially in music.