Over the past three decades, China’s economy achieved one growth miracle by means of another: the expansion of its cities through the migration of hundreds of millions of rural workers.

But that trend is slowly reversing in China’s biggest cities, Beijing and Shanghai, which have announced policies to limit their population. Official figures released last month showed the capital’s residential population in 2017 shrank by 22,000 people.

The drop follows moves last year by Beijing’s local government to cap the city’s population. Officials have outlined plans for the capital’s population to stabilise at 23m “long-term residents” by 2020 to stop what authorities call “urban diseases”, arguing that its water resources could not sustain more people.