The Nigerian economy is one of the largest in Africa. Since the late 1960s it has been based primarily on the petroleum industry. A series of world oil price increases from 1973 produced rapid economic growth in transportation, construction, manufacturing, and government services. Because this led to a great influx of rural people into the larger urban centres, agricultural production stagnated to such an extent that cash crops such as palm oil, peanuts (groundnuts), and cotton were no longer significant export commodities. In addition, from about 1975 Nigeria was forced to import such basic commodities as rice and cassava for domestic consumption. This system worked well as long as revenues from petroleum remained constant, but since the late 1970s the agricultural sector has been in continuing crisis because of the fluctuating world oil market and the country’s rapid population growth. Although much of the population remained engaged in farming, too little food was produced, requiring increasingly costly imports. The various governments (most of them military-run) have dealt with this problem by banning agricultural imports and by focusing, albeit briefly, on various agricultural and indigenization plans.
In the late 1990s the government began to privatize many state-run enterprises—especially in communications, power, and transportation—in order to enhance the quality of service and reduce dependence on the government. Most of the enterprises had been successfully privatized by the beginning of the 21st century, but a few remained in government hands.
Source: britannica.com