Today, about 180,000 people around the world will leave the countryside and move to a city. Humans are becoming urban creatures at an accelerating speed. The United Nations calculates that London’s population took 130 years to grow from 1m to 8m. Bangkok in Thailand took 45 years, Dhaka in Bangladesh 37 and Seoul in South Korea just 25.

Cities are the future. Whether they turn out to resemble the gleaming perfection promised by the Emerald City in the Land of Oz or the dystopian chaos of Blade Runner will depend on the technology and governance of future economic development.