“Believing without belonging” has been the American religious mantra for years, and the real-time effects of that anti-“religion” (or anti-institution?) bias was never so apparent as in the latest American Religious Identification Survey. ARIS 2008 surveyed more than 50,000 Americans about their beliefs and builds on two previous sweeping studies, in 1990 and 2001.

The “Nones” are growing (as we wrote at ReligionLink), going from 8.2 percent in 1990 to 14.2 percent in 2001 and now 15 percent. But the big news may be that New England, sanctuary to the Puritans who helped birth the United States and bequeathed its religious legacy, has now taken over from the Pacific Northwest as the least religiously affiliated section of the country.

But this doesn’t mean more Americans are atheists or even agnostics–just nonreligious, and believing in something, even if they’re not sure what. The number of true nonbelievers remains relatively small: About 1.6 percent of Americans call themselves atheist or agnostic. (On the other hand, the overall number of avowed atheists has grown sharply from 900,000 to 1.6 million since 2001.)

Yes, “Christianity” in raw numbers is shrinking: The percentage of Americans who identify as Christian declined from 86.2 percent in 1990 to 76 percent in the latest ARIS. Not all of that is due to immigration from different faiths, and in fact most immigrants coming to the U.S.–even from Asia and elsewhere–are Christian. 

A look behind the numbers shows that most of the decline is due to the ongoing erosion in mainline Protestantism and that evangelical or nondenominational Protestantism is filling the vacuum.

And not surprisingly, the very “religion-y” religion of Roman Catholicism is taking hits, in spite of Latino immigration. ARIS 2008 confirms the Great Shift from the Northeast and Midwest to the South and West.  

But there has been real erosion, and Cathy Grossman’s report at USA Today has some spectacular graphics that illustrate the changes in the Catholic Church and other groups.

Read the entire report and summaries at the Web site of the Program on Public Values at Trinity College, which conducted the survey.