LAGOS, Nigeria — In a quarter-century, at the rate Nigeria is growing, 300 million people — a population about as big as that of the present-day United States — will live in a country the size of Arizona and New Mexico. In this commercial hub, where the area’s population has by some estimates nearly doubled over 15 years to 21 million, living standards for many are falling.
Lifelong residents like Peju Taofika and her three granddaughters inhabit a room in a typical apartment block known as a “Face Me, Face You” because whole families squeeze into 7-by-11-foot rooms along a narrow corridor. Up to 50 people share a kitchen, toilet and sink — though the pipes in the neighborhood often no longer carry water.
At Alapere Primary School, more than 100 students cram into most classrooms, two to a desk.
As graduates pour out of high schools and universities, Nigeria’s unemployment rate is nearly 50 percent for people in urban areas ages 15 to 24 — driving crime and discontent.
The growing upper-middle class also feels the squeeze, as commutes from even nearby suburbs can run two to three hours.
Last October, the United Nations announced the global population had breached seven billion and would expand rapidly for decades, taxing natural resources if countries cannot better manage the growth.
Nearly all of the increase is in sub-Saharan Africa, where the population rise far outstrips economic expansion. Of the roughly 20 countries where women average more than five children, almost all are in the region.
Elsewhere in the developing world, in Asia and Latin America, fertility rates have fallen sharply in recent generations and now resemble those in the United States — just above two children per woman. That transformation was driven in each country by a mix of educational and employment opportunities for women, access to contraception, urbanization and an evolving middle class. Whether similar forces will defuse the population bomb in sub-Sarahan Africa is unclear.
“The pace of growth in Africa is unlike anything else ever in history and a critical problem,” said Joel E. Cohen, a professor of population at Rockefeller University in New York City. “What is effective in the context of these countries may not be what worked in Latin America or Kerala or Bangladesh.”
Across sub-Saharan Africa, alarmed governments have begun to act, often reversing longstanding policies that encouraged or accepted large families. Nigeria made contraceptives free last year, and officials are promoting smaller families as a key to economic salvation, holding up the financial gains in nations like Thailand as inspiration.