A new study by the Pew Forum on Religion and Public Life [executive summary; full report; New York Times cover story] found that 19.6% of adult Americans answered a question about their current religion by saying they were atheist, agnostic or “nothing in particular.”  In 2007, the figure was 15.3%; in 1972, it was about 7%.

Some relevant quotes from the executive summary:

However, a new survey by the Pew Research Center’s Forum on Religion & Public Life, conducted jointly with the PBS television program Religion & Ethics NewsWeekly, finds that 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 (68%). More than half say they often feel a deep connection with nature and the earth (58%), while more than a third classify themselves as “spiritual” but not “religious” (37%), and one-in-five (21%) say they pray every day. In addition, most religiously unaffiliated Americans think that churches and other religious institutions benefit society by strengthening community bonds and aiding the poor.

With few exceptions, though, the unaffiliated say they are not looking for a religion that would be right for them. Overwhelmingly, they think that religious organizations are too concerned with money and power, too focused on rules and too involved in politics.

The growth in the number of religiously unaffiliated Americans – sometimes called the rise of the “nones” – is largely driven by generational replacement, the gradual supplanting of older generations by newer ones. A third of adults under 30 have no religious affiliation (32%), compared with just one-in-ten who are 65 and older (9%). And young adults today are much more likely to be unaffiliated than previous generations were at a similar stage in their lives.

[T]he percentage of Americans who say they never doubt the existence of God has fallen modestly but noticeably over the past 25 years. In 1987, 88% of adults said they never doubt the existence of God. As of 2012, this figure was down 8 percentage points to 80%.

The growth of the unaffiliated has taken place across a wide variety of demographic groups. The percentage of unaffiliated respondents has ticked up among men and women, college graduates and those without a college degree, people earning $75,000 or more and those making less than $30,000 annually, and residents of all major regions of the country.

When it comes to race, however, the recent change has been concentrated in one group: whites. One-fifth of (non-Hispanic) whites now describe themselves as religiously unaffiliated, up five percentage points since 2007. By contrast, the share of blacks and Hispanics who are religiously unaffiliated has not changed by a statistically significant margin in recent years.

[T]he ranks of the unaffiliated [are not] predominantly composed of practitioners of New Age spirituality or alternative forms of religion. Generally speaking, the unaffiliated are no more likely than members of the public as a whole to have such beliefs and practices.  

For example, roughly three-in-ten religiously unaffiliated adults say they believe in spiritual energy in physical objects and in yoga as a spiritual practice. About a quarter believe in astrology and reincarnation. In addition, nearly six-in-ten of the religiously unaffiliated say they often feel a deep connection with nature and the earth; about three-in-ten say they have felt in touch with someone who is dead; and 15% have consulted a psychic. All of these figures closely resemble the survey’s findings among the public as a whole.

On the other hand, the religiously unaffiliated are less inclined than Americans overall to say they often think about the meaning and purpose of life (53% vs. 67%). They also attach much less importance to belonging to a community of people with shared values and beliefs; 28% of the unaffiliated say this is very important to them, compared with 49% of all adults.