Some scientists are spending a dozen years as a postdoc, and while some find careers elsewhere, others become a sort of 'permadoc,' Nature News says. It notes that of 40,000 postdocs in the US, some 4,000 have been a postdoc for six or more years.
Labor economist Paula Stephan at Georgia State University notes that principal investigators have a strong incentive to rely on postdocs: they are skilled, but low-paid workers.
Others like Shirley Tilghman, the president emerita of Princeton University, have also pointed out problems with the postdoc system and have suggested fixes such as limiting the number of years a scientist may spend as a postdoc or the total number of postdocs, encouraging PIs to rely on staff scientists, and changing the structure of labs to make them smaller.
"We've always been at risk of producing more scientists than we have places for, but the stresses and strains were not harmful in the way they are now," Tilghman tells Nature News. "Some changes will have to happen."