Actually this survey looks less detailed than the last survey I posted here from 2001, but its more recent and shows basically the same trends at the 2001 survey.
Like the 2001 survey, this one shows that Americans change their religious affiliation frequently and that one of the fastest growing groups is the non-religious, or at least religiously unaffiliated, though some of those people may still believe in "God" is some personal fashion.
Some articles:
Many Americans switch religious denominations, study finds
The big winner on the shifting religious scene is the group of "unaffiliated" Americans. Today 16.1 percent of adults fit that category. Among young people 18 to 29, one-quarter are unaffiliated.
It's common for young adults completing education or starting careers to become detached from their faith connection. Other people may become disillusioned with organized religion.
"Scandals and conflicts lead some to distance themselves even though they still hold Christian beliefs," says Darren Sherkat, a sociologist at Southern Illinois University in Carbondale, who has studied the unaffiliated. "A perhaps growing percentage are disaffiliated because they don't hold Christian beliefs."
The survey found that 1.6 percent of adults call themselves atheists and 2.4 percent are agnostics (who consider God to be unknowable). The remaining 12 percent in "unaffiliated" split almost evenly between the secular and the religious, who may practice their faith on their own.
Although this category is growing the fastest, the survey shows that about half of the unaffiliated end up returning to a faith connection. Other research, however, indicates that many young people today are disaffected from Christianity, and religious leaders worry that they won't follow the usual return pattern.
America's Unfaithful Faithful
According to Pew, 28% of American adults have left the faith of their childhood for another one. And that does not even include those who switched from one Protestant denomination to another; if it did, the number would jump to 44%. Says Greg Smith, one of the main researchers for the "Landscape" data, churn applies across the board. "There's no group that is simply winning or simply losing," he says. "Nothing is static. Every group is simultaneously winning and losing."
Here is a link to the original study itself: http://religions.pewforum.org/
The thing that I find most surprising about the data person is that "Mainline" Protestant church affiliation only account for about 18% of the adult population. "Mainline" means the traditional Christian sects, which are also the more moderate. Ironically the newer Christian sects tend to be less moderate, and this is mostly encompassed by Evangelical Christianity, which is 26% of the adult population.
To me this bods poorly for Christianity and religious relations in America, because Evangelical Christianity is growing while traditional (and ironically more moderate) Christianity is shrinking). At the same time the number of non-religious or non-Christians is growing also, so this looks like it is setting up for greater conflict.