If you believe the Silicon Valley sloganeers, we are in a “gig economy,” where work consists of a series of short-term jobs coordinated through a mobile app. That, anyway, is both the prediction of tech executives and futurists and the great fear of labor activists.

But anyone who cares about the future of work in the United States shouldn’t focus too narrowly on the novelty of people making extra money using their mobile phones. There’s a bigger shift underway. That’s a key implication of new research that indicates the proportion of American workers who don’t have traditional jobs — who instead work as independent contractors, through temporary services or on-call — has soared in the last decade. They account for vastly more American workers than the likes of Uber alone.

Most remarkably, the number of Americans using these alternate work arrangements rose 9.4 million from 2005 to 2015. That was greater than the rise in overall employment, meaning there was a small net decline in the number of workers with conventional jobs.

That, in turn, raises still bigger questions about how employers have succeeded at shifting much the burden of providing social insurance onto workers, and what technological and economic forces are driving the shift.