In 1955, Walter Reuther, head of the US car workers’ union, told of a visit to a new automatically operated Ford plant. Pointing to all the robots, his host asked: “How are you going to collect union dues from those guys?” Mr Reuther replied: “And how are you going to get them to buy Fords?” Automation is not new. Neither is the debate about its effects. How far, then, does what Erik Brynjolfsson and Andrew McAfee call The Second Machine Age alter the questions or the answers?

I laid out the core argument last week. I noted that the rise of information technology coincides with increasing income inequality. Lawrence Mishel of the Washington-based Economic Policy Institute challenges the notion that the former has been the principal cause of the latter. Mr Mishel notes: “Rising executive pay and the expansion of, and better pay in, the financial sector can account for two-thirds of increased incomes at the top.” Changing social norms, the rise of stock-based remuneration and the extraordinary expansion of the financial sector also contributed. While it was a factor, technology has not determined economic outcomes.

Yet technology could become far more important. Professor Brynjolfsson and Mr McAfee also argue that it will make us more prosperous; and it will shift the distribution of opportunities among workers and between workers and owners of capital.