In 2002 we reported that the fraction of American adults with no religious preference doubled from 7 to 14 percent during the 1990s. Data from this decade show that the trend away from organized religion continues, albeit at a slower pace. Our analysis of the entire time series, presented at the annual meeting of the American Sociological Association in 2009, led us to the conclusion that the trend probably started earlier than we had thought—probably around 1985, 1986, or 1987—and that our previous estimate of the rate of change was, consequently, too high.

We identified political tension and generational succession as the main sources of the trend away from religious affiliation. In the most recent data—collected in 2006 and 2008, and combined to improve statistical precision—28 percent of political liberals answered “no religion” when asked what their religion was, compared with 15 percent of political moderates, and 5 percent of political conservatives—a gap of 23 percentage points from left to right on the political spectrum. From these contrasts and other supporting tabulations we concluded that the growing identification between organized religion and a conservative social policy agenda was pushing liberals and moderates with weak attachments away from organized religion.

Generational change has two parts. People who were raised without religion from the 1960s onward are less likely than previous generations to acquire a religion in adulthood. For examples, the majority of the small group of people who were born in the 1930s and raised without religion stated a religious preference when they were interviewed as adults, while 24 percent remained without a religious preference through adulthood. In contrast, among people born in the 1960s and raised without religion, 58 percent preferred no religion as adults; among people born in the 1980s and raised without religion, 79 percent prefer no religion now.

The other part of generational change is a trend away from organized religion among people raised with religion. People who were raised with religion from the 1960s onward are also less likely than previous generations to stay with religion in adulthood. Looking to the same cohorts as before, only 4 percent of people born in the 1930s and raised with religion had no religious preference when they were interviewed as adults. In contrast, among people born in the 1960s and raised with religion, 11 percent preferred no religion as adults; among people born in the 1980s and raised with religion, 21 percent prefer no religion now.

These changes have more to do with organized religion in particular than with religion more generally. While affiliation and identification with organized religion has waned, religious belief has not. American adults are as likely to believe in god and life after death now as they were twenty years ago. In 2008 62 percent of American adults entertained no doubts about the existence of god, compared with 64 percent in 1988; 3 percent do not believe in god in any way, compared with 2 percent in 1988. In both 1988 and 2008 88 percent of American believed in life after death.

We call the people who believe in god or an afterlife but do not have a religion “unchurched believers.”  In 2008 11 percent of American adults were unchurched believers, compared to 4 percent twenty years earlier. There is a complementary category of “churched unbelievers”: people who state a religious preference but do not believe in god or life after death. Very few of those who prefer a religion do not believe in god: 3 or 4 percent in any given year. Many of them used to prefer a religion but not believe in life after death. That combination of affiliation and unbelief used to be quite common, but is far less so these days. In the early 1970s 20 percent of American adults had a religious preference but did not believe in life after death; in 2006 and 2008 this figure was 12 percent.

Liberal and younger Americans distanced themselves from organized religion over the last twenty years without giving up their traditional beliefs in god, an afterlife, and other spiritual matters.