Can it be that Americans don’t pray well with others?

The number of people who say they don’t belong to a religion has doubled over the last decade, two major studies show.

Explanations don’t come easily. Some believe Americans bristle at the rules of organized religion and seek spirituality on their own terms. Others say people have long avoided religion but only recently felt at ease admitting it.

“I look inside, where we’re all God,” said accountant Karen Arakelian, 24, a former Catholic who lives in Alexandria, Va. “I don’t follow groups, I don’t look in books. We are divine in our own right.”

For countless personal reasons, 29.4 million people said last year that they skip church, mosque and synagogue up from 14.3 million in 1990, an overall rise from 8 percent to 14 percent of the U.S. population.

That group is so large that if it were its own denomination, it would be the third-largest religion in the United States, behind Catholics (50.8 million) and Baptists (33.8 million).

That’s the word from the American Religious Identification Survey, conducted in 2001 among 50,281 U.S. households by the Graduate Center of City University of New York.

“We call ourselves one nation under God,” said Egon Mayer, a sociologist and the survey’s lead author. “And we assume everybody is under some religious group’s umbrella. This study is a sobering reminder that a lot of folks are standing out there, not under any umbrellas.”

The survey’s results are stark but not altogether startling, said Fred Kniss, an expert on the sociology of religion at Loyola University in Chicago.

“There is a fair amount of research that shows people’s commitment to institutional religion is weakening,” he said.

In fact, researchers at the National Opinion Research Center at the University of Chicago came to similar conclusions, said Tom Smith, a center director.

Over the last 10 years, the center found that the percentage of people who say they have no religious preference doubled, from 7 percent of the population to 14 percent which matches the New York study exactly.

Digging for reasons why this is happening may prove more difficult than detecting patterns.

“I don’t know that anybody is qualified to answer why people don’t connect God under a brand label,” Mayer said.

He does not believe it’s accurate to say these figures show that atheism is on the rise. (Last year, 902,000 people identified themselves as atheists, which wasn’t an option in 1990.)

There’s a difference between not believing in God and not belonging to a religion. Indeed, in the most recent Gallup survey on the subject, last year, 90 percent of Americans said they believed in God.

Mayer guessed that the surge in people unaffiliated with religion might have to do with greater tolerance for diversity in society today: “We are more accepting of single parents, gay people, people who live together without marrying,” he said.

The greater influx of immigrants has also exposed Americans to different religions, he said, and other ways of contemplating spirituality.