Surveys show that the “nones” (those who report no religious affiliation) are a diverse group. The first observation often made is to note that only a small percentage self-identify as atheists or agnostics. For instance, Putnam and Campbell, on page 16 of American Grace, report that only 5 people in their 2006 “Faith Matters Survey” of 3,108 described themselves by either label. But it would be better to look at some larger surveys which addressed this question.
The Pew U.S Religious Landscape Survey of over 35,000 Americans in 2007 found 1.6% responding as atheist, 2.4% as agnostic, and 12.1% selecting “no particular religion” (total nones coming to 16.1%). In analyzing the “no particular religion” group, Pew looked at their responses to another survey question: “How important is religion in your life”? They found about half of this group answered “not at all important” or “not too important” while the rest answered “somewhat important” or “very important”. Pew decided to label these two groups as Secular unaffiliated (6.3% of the total) and Religious unaffiliated (5.8%) for the purpose of summarizing the results on other parts of the survey.
For one more comparison, the 2008 American Religious Identification Survey (with 54,461 respondents) found 0.9% atheist, 0.7% agnostic (out of total nones of 15.0%). It should be noted, however, that the percentage of atheists/agnostics in the survey nearly doubled from a previous 2001 tabulation.
Pew asked respondents if they believed in “God or a universal spirit” expressed by level of certainty. 70% of nones answered affirmatively and 36% were “absolutely certain” (vs. 92% and 71% for all respondents). Even 21% of atheists and 55% of agnostics responded affirmatively (8% and 17% were “absolutely certain”!).
When responding to questions relating to specific religious beliefs and practices (fallibility of scripture, belief in the afterlife and miracles, frequency of prayer), nones generally respond at lower levels than the religiously affiliated (as would be expected), but still show significant degrees of agreement with some questions (55% completely or mostly agree with the statement “miracles still occur today as in ancient times vs. 79% for the total).
Looking through the data for the first time, it’s not obvious to me why many of the nones are nones. The authors of American Grace argue that politics are a big reason. But while the nones skew toward the left on political views, the picture here is again very diverse and there is substantial overlap with the religiously affiliated. Putnam and Campbell focus on some relatively large discrepancies in the younger age cohort to make the case for politics acting as a spur to growth in the nones, and this may be the case. Another factor surely is the growth in adoption of atheism as a worldview, but the numbers here are still small. At this point, it strikes me that the growth in the nones is still underexplained.