One in five U.S. adults do not identify with a specific religion, and the number of Protestants has for the first time dipped significantly below 50 per cent, according to a poll released this week by Pew Research Center.
Pew researchers said the growing ranks of those with no religious affiliation suggests Americans may slowly be becoming less religious. The number of adults who consider themselves atheist, agnostic or "nothing in particular" has increased from about 15 per cent to nearly 20 per cent in the last five years, the highest percentage ever for that group in Pew polling.
Fifty-eight per cent of Americans still say religion is very important in their lives, far exceeding the value given to religion by people in Britain, France, Germany or Spain, Pew said.
The survey also found that many of the country's 46 million adults who don't claim a religion remain religious and spiritual in some way, even though most are not seeking a denomination.
Seventy-three per cent of U.S. adults are Christian, but the number of Protestants dropped to 48 per cent in 2012 from 50 per cent in 2011 and 53 per cent in 2007, the poll showed.
Pew said the findings were based on several surveys, including most recently a national telephone poll of 2,973 adults that was conducted between June 28 and July 9, 2012 and an additional 511 interviews with religiously unaffiliated adults between June 28 and July 10.