This increase is being driven by both population growth and a continued shift towards urbanization, particularly to so called 'megacities' - metropolises that have a population of 10 million or more.

As Statista's Anna Fleck details below, urbanization takes place because of both push and pull factors. The IEA describes how in the Democratic Republic of Congo's capital of Kinshasa, factors pushing people away from rural areas include issues of violence and a general lack of security, the presence of criminal groups, lack of policing, ecological degradation, and the fact there are too many people for the available agricultural land. Meanwhile, a pull factor could be the attraction of an increase in the standard of living.

There are currently 33 megacities worldwide. Tokyo (37.3 million), Delhi (32.3 million), Shanghai (28.7 million), Dhaka (22.6 million), São Paulo (22.5 million) and Mexico City (22.1 million) take the lead as the most populous of these. By 2050, 14 more cities are set to join their ranks, with a total increased population of some 213 million people. The new order will then become Delhi (49.6 million), Dhaka (34.6 million), Tokyo (32.6 million), Cairo (32.6 million) and Mumbai (32.4 million).

In addition to a rise in the number of people living in these cities, the countries themselves will also likely see economic growth.

According to AXA, Manila in the Philippines and Bangalore in India are expected to see close to 150 percent GDP growth by the end of the decade.