Data shows participation in the past few years has fallen mainly because Americans have retired or signed up for disability benefits.

“The data suggest that the recent exits from the labor force have been more voluntary in nature than was the case in 2009, when the economy was weak and job prospects were dire,” said Omair Sharif, senior economist at RBS in Stamford, Connecticut.

According to economists who have analyzed Labor Department data, 6.6 million people exited the workforce from 2010 and 2013. About 61 percent of these dropouts were retirees, more than double the previous three years’ share.

People dropping out because of disability accounted for 28 percent, also up significantly from 2007-2010. Of those remaining, 7 percent were heading to school, while the other 4 percent left for other reasons.