By the end of the century, Africa will be home to 40% of the world’s population – and nowhere is this breakneck-pace development happening faster than this 600-mile stretch between Abidjan and Lagos.

t has long been said that no one knows with any certainty the population of Lagos, Nigeria. When I spent time there a decade ago, the United Nations conservatively put the number at 11.5 million, but other estimates ranged as high as 18 million. The one thing everyone agreed was that Lagos was growing very fast. The population was already 40 times bigger than it had been in 1960, when Nigeria gained independence. One local demographer told me that 5,000 people were migrating to Lagos every day, mostly from the Nigerian countryside. Since then, the city has continued to swell. By 2035, the UN projects that Lagos will be home to 24.5 million people.

What is happening in Lagos is happening across the continent. Today, Africa has 1.4 billion people. By the middle of the century, experts such as Edward Paice, author of Youthquake: Why Africa’s Demography […]