To work is human: it has always been one of the defining characteristics of life. Yet today 47% of American employment is at risk of automation within the next two to three decades, while professional work in law, medicine and accounting is or soon will be at risk. Drawing on research from around the world - from Volvo's operations in Sweden to a vast Foxconn production facility in Shenzhen, via Indian development economists and Silicon Valley venture capitalists - Economist correspondent Ryan Avent investigates what this revolution in the world of work means not only for our economies but also our societies.