A major feature of Nigeria's economy in the 1980s, as in the 1970s, was its dependence on petroleum, which accounted for 87 percent of export receipts and 77 percent of the federal government's current revenue in 1988. Falling oil output and prices contributed to another noteworthy aspect of the economy in the 1980s—the decline in per capita real gross national product, which persisted until oil prices began to rise in 1990. Indeed, GNP per capita per year decreased 4.8 percent from 1980 to 1987, which led in 1989 to Nigeria's classification by the World Bank as a low-income country (based on 1987 data) for the first time since the annual World Development Report was instituted in 1978. In 1989 the World Bank also declared Nigeria poor enough to be eligible (along with countries such as Bangladesh, Ethiopia, Chad, and Mali) for concessional aid from an affiliate, the International Development Association (IDA).