One wonders: What happened in 1988?
A new survey, done by the University of Chicago and analyzed by sociologists from UC Berkeley and Duke, puts the religiously unaffiliated at 20 percent of the American population. Atheists, meanwhile, come in at about 3 percent, and don't seem to be growing.
Elizabeth Drescrer writes:
The report makes clear that the trend away from affiliation with organized religion is not an indication of declining religious belief. They write that “conventional religious belief, typified by belief in God, remains very widespread—59 percent of Americans believe in God without any doubt,” adding that, “Atheism is barely growing,” with 1% in 1962 and 3% in 2012 indicating no belief in God.
Also interesting: even though we've now seen two decades of rapidly growing disaffiliation, the number of those raised outside of religious organizations is still very, very small. Only 8 percent say they were raised without religion. This could be connected to fact that people tend to get more religious when they have children. David E. Campbell and Robert D. Putnam point this out in American Grace. For each generation since the '60s, religious affiliation has increased at about the time that generation has children.
For those who came of age in the '60s, for example, about 12 percent said they had no religious preference in the mid-'70s. By 1985, though, that number had dropped to about 8 percent. In fact, that generations' irreligion only rose again in the early 2000s, around the time their children came of age. By the end of the 2000s, the generation that came of age in the '60s was again as likely to profess no religious preference as they had been in the mid-'70s. That trend holds for each successive generation. For those who came of age in the 2000s, for example, irreligion spikes in the first few years of the millennium (possibly for historical reasons, rather than generational ones) to the point that 30 percent said they didn't have a religious preference. But then that number drops. By the late 2000s, 25 percent say they have no religious preference. They're still, of course, a lot less religious than previous generations, but it seems that even a lot of that 25 percent will raise their children with a religious preference.
All the normal caveats about misinterpreting and over-interpreting this data from this new study apply. What we might be looking at, here, is the waning usefulness of the term "religion."
The question asked, specifically, was: "What is your religious preference? Is it Protestant, Catholic, Jewish, some other religion, or no religion?" That's slightly different that the question asked by Pew, and the difference in the phrasing of the question could account for the difference in answers.