Early in his first term Barack Obama joked that he would “keep an eye on the robots in case they try anything”. He should have known resistance is futile. During Mr Obama’s presidency, IBM’s Watson computer defeated human contestants on the gameshow Jeopardy!, drones have become America’s weapon of choice, the driverless car is now a reality and the word “app” has been detached from its origin. No longer the realm of science fiction, the rise of robots now poses the central economic dilemma of the Obama era.

With each month, the US economy becomes steadily more automated. In January the US economy added just 4,000 manufacturing jobs, and the net increase since July is zero. Yet last month, manufacturing activity rose by its fastest rate since April, according to the Institute for Supply Management. The difference boils down to robots, which pose an increasingly nagging paradox: the more there are, the better for overall growth (since they boost productivity); yet the worse things become for the middle class. US median income has fallen in each of the past five years.

Things cannot continue as they are. Yet change is speeding up. Manufacturing employment is shrinking around the world. China is moving even faster towards industrial robotics, an area in which German and Japanese manufacturers dominate. Last year Foxconn, the Shenzhen-based assembler for Apple, Nokia and others, said it was buying 1m robots in the next three years to substitute for workers performing repetitive manual tasks. At the other end of the spectrum, a restaurant in Harbin, northern China, last year became the first to be entirely waited on by robots. Last month, China opened the world’s first museum of 3D printing.