Nigeria is Africa's biggest oil producer and most populous country - but poverty is widespread and the country is in the grip of a violent uprising by Islamists Boko Haram. The BBC maps the country's divisions ahead of its postponed elections.
President Goodluck Jonathan came to power with the People's Democratic Party (PDP) in 2011 after winning 59.6% of the vote - with most support in the mainly Christian and animist south - while former military ruler Muhammadu Buhari had most backing in the largely Muslim north. It was the first time a vote had split the country along these lines. Defections by state governors have since changed the country's political map.
Nigeria's 160 million population is also divided among numerous ethno-linguistic groups. The Hausa-Fulani people, based in the north are mostly Muslims. The Yorubas of the south-west are split between Muslims and Christians and the Igbos of the south-east and neighbouring groups are mostly Christian or animist. Most Boko Haram fighters are ethnic Kanuris.
Oil and gas accounts for 35% of Nigeria's GDP - and pays for 70% of government spending. Petrol products account for 90% of the country's export earnings.
But the recent fall in oil prices has forced the government to revise its budget, and cut growth forecasts. For the first time since 1999, Nigeria's government revenue is shrinking and the value of the national currency, the naira, is falling.
Poverty is still widespread in Nigeria, despite the country's recent boom years. According to the national bureau of statistics, almost two-thirds of the population lived in absolute poverty - ie without basic needs like food, safe drinking water and shelter - in 2009-10.
The problem is worst in the north - Jigawa state has the highest poverty rate, of 88.5%, while in Sokoto it is 86%.
The northern half of the country also has the lowest take-up of childhood vaccinations. In the north-western state of Sokoto, only 1.4% of children aged 12-23 months had received all their basic vaccinations, including BCG, measles, DPT and polio.
According to the 2013 demographic and health survey, the country's nine most northerly states all have vaccination rates below 15%. Some northern groups have boycotted immunisation programmes in the past, saying they were a Western plot to make Muslim women infertile.
However, more recently the country has been making good progress. The Global Eradication Initiative says that January 2015 marked six months since the last case of polio in the country.
Literacy is seen as one of the keys to raising living standards for the next generation. Again the north/south divide is evident, with lower school attendance across northern Nigeria. The percentage of pupils aged 13-18 attending secondary school is only 12.3% of students in Yobe.
Boko Haram has attacked schools teaching Nigeria's national curriculum, which the militants regard as too Western. In one of the worst attacks last year, more than 200 schoolgirls were abducted from a boarding school in Chibok in April.
Boko Haram promotes a version of Islam which makes it "haram", or forbidden, for Muslims to take part in any political or social activity associated with Western society.
A state of emergency was declared in May 2013 in the northern states where Boko Harma is strongest, Borno, Yobe and Adamawa.
The Islamist group now controls much of Borno state and some other areas, where it will be impossible to hold the election.
Analysts say the threat from Boko Haram will disappear only if Nigeria's government manages to reduce the region's chronic poverty and builds an education system which gains the support of local Muslims.