Imagine a society where everything you do, say and buy is monitored and evaluated by the authorities – a society where citizens are ranked according to good or bad behaviour. In China, this Orwellian scenario is becoming reality. The country is implementing a “social credit” rating system, made possible thanks to the mass collection of data on its citizens. It’s set to be implemented nationwide in 2020. But the scheme is already being tested in some Chinese cities. Our correspondents report.