China’s four great inventions are known as papermaking, printing, gunpowder and the compass. That list leaves out China’s most influential invention: the examination system. The system can be living hell for exam takers, but it is arguably the least bad mechanism for selecting talent, which helps to explain why it has spread to the rest of the world.

Exams were invented during the Sui dynasty (581–618) as a means of selecting public officials based on merit. The imperial examination system, keju, was perfected in the Song dynasty (960–1279), when concerns for fairness led to the invention of anonymous grading (exams were rewritten so the graders could not recognise the candidates’ handwriting). In the Ming dynasty (1368–1644), regional quotas were set to ensure that exam takers from the poorer parts of China would have some chance of success.

For the next few centuries, examinations served as the main mechanism for the recruitment of public officials in China (with the exception of the emperor). But the system became corrupt, rigid and out of date, and it was abolished in 1905. Not coincidentally, the whole imperial system collapsed a few