Forty-four percent of Americans have either switched their religious affiliation since childhood or dropped out of any formal religious group, according to the largest recent survey on American religious identification. ...

"Constant movement characterizes the American religious marketplace, as every major religious group is simultaneously gaining and losing adherents," the U.S. Religious Landscape Survey said.

The survey also concluded that 16 percent of American adults are not affiliated with any faith today. About 4 percent describe themselves as atheist or agnostic. Young adults ages 18 to 29 are much more likely than people 70 and older to say they are unaffiliated with any particular religion, Pew found.