The technological strides of the past few decades have contributed to the nation’s rising income inequality, they argue, because only a small group of people tends to benefit income-wise from inventing the next iPhone or tax-preparation software. And Brynjolfsson and McAfee believe the biggest labor-market effects have yet to be felt. A separate 2013 study by Oxford University researchers Carl Benedikt Frey and Michael A. Osborne might give a taste of what’s to come; Frey and Osborne say that nearly half of American jobs are at “high risk” of being taken over by robots in the next decade or two. Economists take this idea seriously, and it has a number of policy implications, particularly when it comes to higher education.

But while this futuristic scenario is scary or exciting, depending on your point of view, a number of liberal economists argue that there’s just no evidence yet that this is the course the economy will chart. “If technology is leading us to generate more output with fewer workers, that should show up in higher productivity, and you don’t really see that,” says Jared Bernstein, a former economic adviser to Vice President Joe Biden who is now a senior fellow at the liberal Center on Budget and Policy Priorities. “Isn’t that kind of intuitive?”

“The effects of new machine technology are not showing up in productivity statistics—at least not yet—and productivity is by far the most important driver of long-term economic growth,” Christine Lagarde, managing director of the International Monetary Fund, said last week. “We certainly need to keep an eye on this.”