The economy of Nigeria historically was based on agriculture, and about 70% of the workforce is still engaged in farming (largely of a subsistence type). The chief crops are cocoa, peanuts, palm oil, corn, rice, sorghum, millet, soybeans, cassava, yams, and rubber. In addition, cattle, sheep, goats, and pigs are raised.
Petroleum is the leading mineral produced in Nigeria and provides about 95% of foreign exchange earnings and the majority of government revenues. It is found in the Niger delta and in the bights of Benin and Biafra. Petroleum production on an appreciable scale began in the late 1950s, and by the early 1970s it was by far the leading earner of foreign exchange. The growing oil industry attracted many to urban centers, to the detriment of the agricultural sector, and the huge government revenues from oil led to widespread corruption that has continued to be a problem. In the 1980s a decline in world oil prices prompted the government to bolster the agricultural sector. Nonetheless, both refinery capacity and agriculture have not kept pace with population growth, forcing the nation to import refined petroleum products and food. Other minerals extracted include tin, iron ore, coal, limestone, columbite, lead, zinc, and gold.
Industry in Nigeria includes the processing of agricultural products and minerals, and the manufacture of textiles, construction materials, footware, chemicals, fertilizer, and steel. Fishing and forestry are also important to the economy, and there is small commercial shipbuilding and repair sector. In addition, traditional woven goods, pottery, metal objects, and carved wood and ivory are produced. Nigeria's road and rail systems are constructed basically along north-south lines; the country's chief seaports are Lagos, Warri, Port Harcourt, and Calabar.
Except when oil prices are low, Nigeria generally earns more from exports than it spends on imports. Other important exports include cocoa, rubber, and palm products. The main imports are machinery, chemicals, transportation equipment, manufactured goods, food, and live animals. The United States is by far the largest trading partner, followed by China, Brazil, Spain, and Great Britain.