REM

The U.S. religious marketplace is extremely volatile, with nearly half of American adults leaving the faith tradition of their upbringing to either switch allegiances or abandon religious affiliation altogether, a new survey finds.

The study released Monday by the Pew Forum on Religion and Public Life is unusual for its sheer scope, relying on interviews with more than 35,000 adults to document a diverse and dynamic U.S. religious population.

While much of the study confirms earlier findings — mainline Protestant churches are in decline, non-denominational churches are gaining and the ranks of the unaffiliated are growing — it also provides a deeper look behind those trends, and of smaller religious groups.

"The American religious economy is like a marketplace — very dynamic, very competitive," said Luis Lugo, director of the Pew Forum. "Everyone is losing, everyone is gaining. There are net winners and losers, but no one can stand still. Those groups that are losing significant numbers have to recoup them to stay vibrant."

The U.S. Religious Landscape Survey estimates the United States is 78 percent Christian and about to lose its status as a majority Protestant nation, at 51 percent and slipping.

More than one-quarter of American adults have left the faith of their childhood for another religion or no religion at all, the survey found. Factoring in moves from one stream or denomination of Protestantism to another, the number rises to 44 percent.

One in four adults ages 18 to 29 claim no affiliation with a religious institution.

"In the past, certain religions had a real holding power, where people from one generation to the next would stay," said Penn State University sociologist Roger Finke, who consulted in the survey planning. "Right now, there is a dropping confidence in organized religion, especially in the traditional religious forms."