It used to be that when someone said they were working for a company, it was a pretty safe bet that they were a full-fledged employee, with all the rights and benefits that come along with that status.

But that’s no longer the case. Economists Lawrence Katz of Harvard and Alan Krueger of Princeton found in a 2016 study that the proportion of U.S. workers who do their jobs on a contingency basis hit 15.8 percent in late 2015, up from 10.1 percent in February 2005. The percentage hired through contract companies rose the most, to 3.1 percent in 2015 from just 0.6 percent 10 years earlier.