Despite the fact that the mainstream media likes to write a lot of stories how religious revival in the United States one of the great unreported facts of the last 15 years is the rise of the proportion of Americans who are not affiliating with any religion. The reason this isn't reported much is that it won't sell that much copy; the irreligious by their nature don't get that excited by irreligion. In contrast religious people want to read about how religion is on the rise. There will always be stories about how religion & science dovetail in the media because that sells magazines; the fact that 9 out of 10 National Academy of Science members are atheists or agnostics won't sell magazines, and might even make scientists a little worried about the funding pipeline.
The US Religious Landscape Survey by Pew doesn't come burdened by the need to satisfy the consumer market. From chapter 2:
The biggest gains due to changes in religious affiliation have been among those who say they are not affiliated with any particular religious group or tradition. Overall, 7.3% of the adult population says they were unaffiliated with any particular religion as a child. Today, however, 16.1% of adults say they are unaffiliated, a net increase of 8.8 percentage points. Sizeable numbers of those raised in all religions - from Catholicism to Protestantism to Judaism - are currently unaffiliated with any particular religion.
...
The unaffiliated group provides a good example of the high degree of religious movement that has taken place in the U.S. Overall, 3.9% of the adult population reports being raised without any particular religious affiliation but later affiliating with a religious group. However, more than three times as many people (12.7% of the adult population overall) were raised in a particular faith but have since become unaffiliated with any religious group.
Here are some breakdowns:
Percentage of Adults Entering and Leaving Each Group
Childhood Religion Entering Group Leaving Group Current Group
Atheist0.5+1.4-0.31.6
Agnostic<0.3+2.3-<0.32.4
Nothing in particular 6.6+9.6-4.112.1
But do note that not all unaffiliated people are atheists are agnostics, in fact, the majority are not. The Pew study notes that this unaffiliated group is divided between those who are secular (religious sentiments are not important) and those who are believers of some sort, if not affiliated (one could term these the "spiritual" segment). Below are some tables of interest from the Pew study.
Age Distribution
18-2930-4950-6465+
All unaffiliated 3140208
Atheist37361612
Agnostic3434229
Secular unaffiliated 2941218
Religious unaffiliated 3043207
Education
Less than High School High School Some College CollegeGraduate School
All Americans 1336231611
All unaffiliated1334241613
Atheist828232121
Agnostic522292320
Secular unaffiliated 1035241713
Religious unaffiliated 214022116
Income
< $30 K $30 - $50 K $50 - $100 K > $100 K
All Americans 31223018
All unaffiliated 29232919
Atheist21203128
Agnostic18223525
Secular unaffiliated 25243021
Religious unaffiliated 40242512
Sex
MaleFemale
All Americans 4852
All unaffiliated 5941
Atheist7030
Agnostic6436
Secular unaffiliated 6040
Religious unaffiliated 5248
Marital Status
MarriedPartnerDivorced/SeparatedWidowedNever Married
All Americans 54612819
All unaffiliated461012328
Atheist391110337
Agnostic411010336
Secular unaffiliated 491111326
Religious unaffiliated 471013425
Number of children under age 18 living at home
0123+
All Americans 6513139
All unaffiliated 6713137
Atheist7511105
Agnostic751194
Secular unaffiliated 6715135
Religious unaffiliated 60141412
Notice a trend? There is a spectrum of in terms of the clustering of demographic profiles, atheist & agnostics are at one end, and the "religious" unaffiliated at the other. In fact, in many ways the non-religious Americans who still exhibit a spiritual orientation are more like the typical American than they are like atheists or agnostics (with the secular, but still theist, group in the middle). In some characteristics, such as income and education, the spiritual segment is very different from the atheist & agnostic group, because attainment or level is below the American median for the former but above for the latter. What's the explanation? I think it probably has do with an alienation from bourgeois orientation of American religion on the part of some lower and working class sectors. Think the mullet/wife-beater/Ricki Lake demographic. Religion and god are actually different things on a fundamental level, and atheists & agnostics reject the latter, which as a necessity usually implies rejection of the former, but many Americans who reject the former do not turn away from the latter.
This shouldn't be too surprising. Secularization is happening in the United States, just a few generations after Europe, so the European model, where the proportion of atheists and non-affiliated theists increases over time is probably a good trend to bet on. And as I've noted before, though Europe is post-Christian it is not atheist.
