Poll after poll demonstrates that the number of religious people in America is declining--even Bill O'Reilly now admits it. But counting the corresponding increase of those without traditional religion continues to be a mix of moving targets and differing definitions. This is because people are often counting different groups.
Some just want to know how many antitheists there are out there, those who aren't just nonreligious, but are also actively opposed to religion. But that group of Christopher Hitchens-admiring crusaders is actually just a comparatively tiny segment of the overall group. In fact, there are really two overlapping primary communities of those who do not identify with a traditional religion.
IDENTITY
On the one hand, you have those who don't identify with any particular religion and thus see themselves as secular. This number has risen the highest, to 22.8 percent of the US population, or 56 million, according to the latest Pew Forum report called America's Changing Religious Landscape, and includes those who choose "none of the above" when asked what religion they identify with. That's a higher number than the number of Catholics. That's more than triple the number of non-Christian religious people.
Some in the media and general public would be surprised to discover that one's choice not to identify with religion doesn't necessarily speak to the issue of belief. Some seculars (30 percent of them) say religion is very or somewhat important to them. Some of them do believe in a god and may be quite devout in that belief. There's a particular trend in northwest America where groups have eschewed traditional religious institutions in order to gain a more direct connection to God. It's possible that they make up a significant portion of this segment.
While a significant number of the "nones" are believers who don't choose to identify with a traditional religion, a majority of them aren't. According to Pew, this group also includes all those (some 31 percent of this group or 8 percent of all Americans) who identify as atheists and agnostics first, as well as a number of deists and freethinkers who have no interest in religion. According to Pew, 88 percent of the nones aren't searching for religion either, so this isn't the fertile ground for future converts that some hopeful religious people think. Groups like Openly Secular seek to corral this group and give them the acceptance they deserve.
BELIEF
On the other hand, there are those who are defined by their nonbelief. They aren't convinced that there's a god or other supernatural force at work in our daily lives and prefer personal action over prayer. Such convictions are centered on where we get our facts. For nontheists, we don't get knowledge from ancient books like the Bible or divine revelation (as Pat Robertson claims to get), but instead from observation, analysis, and experience. This is what most people likely mean, when they are trying to count us atheist and agnostic humanist types, but studies haven't done a great job accounting for it.
Some in the media and general public would be surprised to discover that many such people do identify with traditional religion even if they aren't believers. While the latest Pew Poll didn't compare beliefs, an earlier 2008 one did (see pages 162-164) and found that hundreds of thousands of Catholics are essentially certain there's no god, and fully 29 percent of them see God as only an impersonal force. A significant percentage of those who identify with any of the mainline religions are atheists by definition, with many more believing in an impersonal God--as high as half of all Jews and Buddhists. Since 5 percent of the overall polled didn't believe in god and another 25 percent just believed in the impersonal God, with the intervening decline in religiosity, think how much higher those numbers must be today!
And if we look at belief and not just identity, there are three million (beyond the 22.8 percent unaffiliated and beyond the nonbelievers in traditional religions) who identify with what Pew calls "other faiths," which is composed of mostly nontheistic traditions: Unitarians, deists, humanists, Ethical Culturists, Humanistic Jews and others.
So how big is this community really? We don't know for sure, but considering the reported numbers and the fact that people underreport concealable identities that face prejudice, it's likely that about one in four Americans are not religious, at least in the traditional sense. It's time to separately recognize the growth of both the nonreligious and the nonbelievers and better accommodate both in public life.