Washington, DC (CNN Business) It was one of the most striking findings of 2016: The share of workers in "alternative" work arrangements, such as Uber drivers and other independent contractors, had risen dramatically over the previous decade.

The gig economy was exploding. The study from two well-known economists seemed to confirm that the traditional employment relationship was on the way out, to be replaced by micro-tasks delivered on demand.

Now the authors of that study — Alan Krueger of Princeton University and Larry Katz of Harvard — have walked back its conclusion s . Their new study, released Monday, shows the challenge of figuring out how much Uber-type jobs have changed the landscape of American work.

Katz and Krueger's 2016 paper, based on data collected with the RAND Corporation, attempted to replicate the US Bureau of Labor Statistics' 2005 contingent worker supplement. At the time the Labor Department, the parent agency of BLS, didn't have the money to field a new survey itself.

The finding by Katz and Krueger was a blockbuster: They found that 15.8% of workers were in some kind of alternative work situation — from temporary help companies to the self-employed — up from 10.7% in 2005.

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