The uninhabited islands were discovered and colonized by the Portuguese in the 15th century; Cabo Verde subsequently became a trading center for African slaves and later an important coaling and resupply stop for whaling and transatlantic shipping. The fusing of European and various African cultural traditions is reflected in Cabo Verde’s Crioulo language, music, and pano textiles. Following independence in 1975, and a tentative interest in unification with Guinea-Bissau, a one-party system was established and maintained until multi-party elections were held in 1990. Cabo Verde continues to sustain one of Africa's most stable democratic governments. Repeated droughts during the second half of the 20th century caused significant hardship and prompted heavy emigration. As a result, Cabo Verde's expatriate population is greater than its domestic one. Most Cabo Verdeans have both African and Portuguese antecedents. Cabo Verde’s population descends from its first permanent inhabitants in the late 15th-century – a preponderance of West African slaves, a small share of Portuguese colonists, and even fewer Italians, Spaniards, and Portuguese Jews. Among the nine inhabited islands, population distribution is variable. Islands in the east are very dry and are only sparsely settled to exploit their extensive salt deposits. The more southerly islands receive more precipitation and support larger populations, but agriculture and livestock grazing have damaged their soil fertility and vegetation. For centuries, the country’s overall population size has fluctuated significantly, as recurring periods of famine and epidemics have caused high death tolls and emigration.