"The most striking trend of recent decades has been the major increase in the number and the proportion of adults who profess no religion," wrote the authors of the American Religious Identification Survey (ARIS).
The disaffected tended to be young: Of respondents under 35 years of age, 23 percent of the men and 18 percent of the women said they did not follow any organized faith.
"Look at Europe, where a secular trend is prevalent," said Ariela Keysar, a demographer at Trinity College in Hartford, Conn., and the study’s co-author. "We’re not there, but we’re going in that direction."
Another finding that the researchers said surprised them: 43 percent of the unaffiliated were former Roman Catholics.
They were a disproportionately large presence in those ranks, given that Catholics make up slightly less than one-quarter of the general population in the United States.
"Why aren’t Catholics becoming Baptists or something else?" Keysar said. "Instead, they are deciding to distance themselves from organized religion. So there is something major going on" in Catholic religious identity, she said. "It’s in transition."
For the ARIS study, telephone pollsters queried randomly chosen households across the country in 2001. They began with a question they had first posed in 1990 during a survey of 110,000 households: "What is your religion?" (The Census Bureau, which is forbidden by law to ask religious identity, references the earlier survey on its Web site.)
The more recent ARIS survey found that 19 percent of baptized Catholics leave the church, compared with an average of 16 percent for Americans of all faiths.
But an exceptionally large number of Catholics who drop out – 28 percent – do not join another faith. The next largest group to quit not only their church but religion entirely are Methodists, at 17 percent.
The ARIS study did not collect anecdotal information that might explain why Americans are leaving organized religion, or why such a large proportion of Catholics are among them. Keysar said the authors hoped to study secularization and denomination-switching patterns in detail in a national survey planned for 2010.
Neither topic has been the subject of significant surveys, experts say.
One study conducted in the 1960s suggested that when people leave one denomination, Keysar said, "they’re usually looking for something similar."
If accurate this is not exactly surprising. Poor catechesis combined with Catholic families that don’t integrate their faith into their life other than to go to Mass on Sundays are not exactly inspiring examples of the importance of the faith.