A complex pattern of wealthy and poorer areas develops, with wealthier middle-class people moving to the suburbs and poorer people, including foreign immigrants, left behind
New shops and services may open in the city as people move back, boosting the local economy and creating jobs, but original residents may not be able to afford to live in the area anymore
Megacities dominate the national and regional economies of countries because companies choose to build their headquarters in cities with a large number of skilled workers and good transport links
The number of world cities is increasing, with more recent economic growth in countries like Nigeria allowing cities like Lagos to become contenders for world city status