Business Insider reports the world's projected fastest-growing cities based on UN population estimates are all on one continent.
The world population is expected to grow to 8.6 billion in 2030, and African metro areas are leading this growth.
Africa is growing so quickly because of its increasingly large young population, the highest of any continent.
Over 75% of its population is younger than 35.
The world's third fastest-growing city is Kampala, Uganda.