Millions of Americans are joining the freelance ranks, and more of them are opting to remain in that status long-term than ever before.

That's according to the sixth annual Freelancing in America study, published on Thursday by hiring platform Upwork and the nonprofit Freelancers Union. In a survey of 6,001 U.S. working adults--a mix of freelancers and full-time employees--the study's sponsors found that 50 percent of freelancers now view working independently as a permanent career choice, rather than a temporary way to make money. The study also notes that 10 million more Americans consider themselves long-term freelancers now than they did five years ago.

Much of the shift is due to evolving societal perceptions, with a majority of survey respondents saying top professionals in their industry have increasingly chosen to work independently over the past three years.

Freelancing is especially common among younger workers, the study found. More than half of U.S. workers aged 18 to 22 freelanced during the past year, an all-time high for any age group since Upwork and Freelancers Union started tracking data in 2014. That's compared with 40 percent of workers aged 23 to 38, 31 percent of workers aged 39 to 54, and 29 percent of workers aged 55-plus.

"With a strengthening labor market, we will increasingly see people work on the terms that they prefer," Adam Ozimek, Upwork's chief economist, said in a statement. "These compositional shifts will be important to understand as we near full employment."