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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 has proved computers can outfox the most agile minds, 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,...