WASHINGTON — 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. The survey, released yesterday by the Pew Forum on Religion and Public Life, found that Americans’ faith identity fluctuates during their lives, with vast numbers moving away from the faith tradition of their childhood to embrace other religious traditions — or no faith at all. The survey interviewed 35,000 people.

Among other findings, the survey indicated that members of Protestant denominations now make up only a slight majority — 51.3% — of the adult population. The 44% figure includes people who switch affiliations within one of the major faith traditions, such as a Protestant who goes from Baptist to Methodist. Counting only people who switch traditions altogether — say, from Catholic to Orthodox, or Protestant to Muslim — the number drops to 28%. “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% of American adults are not affiliated with any faith today. About 4% 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.

“America has always been very diverse [religiously], but it is diverse in a very different way now because we have more different religious traditions,” John Green, a senior fellow in religion and American politics for the Pew Forum, said. “Somebody raised in 1900 could be a Catholic or various kinds of Protestants … today, of course, one has available Islam and Buddhism and Hinduism as well as all those differences between Protestants that used to exist, and maybe a few different ones that didn’t exist around 1900.”