The United Nations estimates that the population of Nigeria in  was at , distributed as 51.7% rural and 48.3% urban, and with a population density of 167.5 people per square kilometre. Around 42.5% of the population were 14 years or younger, 19.6% were aged 15–24, 30.7% were aged 25–54, 4.0% were aged 55–64, and 3.1% were aged 65 years or older. The median age in 2017 was 18.4 years. Nigeria is the seventh most populous country in the world. The birth rate is 35.2-births/1,000 population and the death rate is 9.6 deaths/1,000 population as of 2017, while the total fertility rate is 5.07 children born/woman. Nigeria's population increased by 57 million from 1990 to 2008, a 60% growth rate in less than two decades.  Nigeria is the most populous country in Africa and accounts for about 17% of the continent's total population as of 2017; however, exactly how populous is a subject of speculation.