The religiously unaffiliated includes more than 13 million self-described atheists and agnostics as well as nearly 33 million people who say they have no particular religious affiliation, the Pew Forum on Religion and Public Life survey released Tuesday indicated.
The number of those who said they aren't affiliated with a particular religion increased from just more than 15 percent to just less than 20 percent of all U.S. adults in the past five years, the survey indicated.
The survey by the Pew Research Center's Forum on Religion and Public Life, conducted jointly with the PBS television program Religion & Ethics NewsWeekly, found many of the country's 46 million unaffiliated adults are religious or spiritual in some way. Two-thirds of them say they believe in God and more than half said they often feel a deep connection with nature and the earth. A third said they were "spiritual" but not "religious" and about a fifth said they pray daily.
In addition, most religiously unaffiliated Americans said they think religious institutions benefit society by strengthening community bonds and aiding the poor.
The growth in religiously unaffiliated Americans -- sometimes called the "nones" -- is mainly driven newer generations replacing older ones, Pew said. The survey found a third of adults less than 30 years of age have no religious affiliation compared with one-in-10 65 years and older.
Pew said today's young adults also are more likely to be unaffiliated than previous generations were at a similar life stages.
The report is based on a nationwide survey by the Pew Research Center conducted June 28-July 9 of 2,973 adults. In partnership with Religion & Ethics NewsWeekly, the Pew Forum conducted an additional 511 interviews with religiously unaffiliated adults June 28-July 10, for a total sample of 958 religiously unaffiliated respondents in the survey. A margin of error was unavailable.