Nones

It has frequently been noted that religious belief in the United States is in decline and that the trajectory is similar to that experienced in the late-19th and 20th century Western Europe. According to what's called the "Secularization Hypothesis," as a nation becomes more advanced and prosperous it will inevitably become more secular.

The most recent General Social Survey of religious affiliation in the United States seems to confirm that something like this is happening here. According to a couple of articles on the GSS findings (see here and here),

The number of Americans who identify as having no religion has risen 266 percent since 1991, and is now statistically tied with the number of Catholics and Evangelicals.

People with no religion – known as 'nones' among statisticians – account for 23.1 percent of the U.S. population, while Catholics make up 23 percent and Evangelicals account for 22.5 percent, according to the General Social Survey.

Those three groups now represent the largest three religious groups in America.

It appears from the chart that much of the rise of the "Nones" has come at the expense of what's called mainline, or liberal, Protestantism. As the "Nones" have ascended, the number of mainline Protestant Christians has fallen 62.5 percent since 1982, to now account for just 10.8 percent of the U.S. population, according to the survey.

The trend is not being fueled by a rise in atheism which is still relatively rare and not much more common than it was in the 1990s - somewhere between 3 and 4% of the population.

Evangelicalism (a more conservative protestantism) and Catholicism seem to be down but not much. The stability of the numbers of Catholics is really quite remarkable given the scandals that have rocked the Catholic church in recent years.

Another interesting aspect of the report is that religious affiliation seems to track political affiliation, or vice versa:

Political conservatives identify far more with organized religion than political liberals do; political moderates fall between them in religious identification, as they do in politics. In 2014, 9 percent of political conservatives had no religious preference compared to 19 percent of political moderates and 38 percent of political liberals.

In 1990, 5 percent of conservatives, 6 percent of moderates, and 15 percent of liberals had no religious preference. Hout and Fischer wrote extensively about this trend in their 2014 article in the Sociological Science, pointing to political polarization and generational succession as the keys to understanding the trend in religious preferences.

The alliance between conservative politicians and the leadership of conservative religious denominations was pushing political liberals who had been raised in conservative denominations away from organized religion.

This may be true, but it doesn't seem to explain why the heaviest losses are in the most liberal denominations while the more conservative groups seem to be holding fairly steady. As mentioned above, though, whatever is going on it doesn't seem that belief in God is declining significantly:

Conventional religious belief, typified by belief in God, remains very widespread — 59 percent of Americans believe in God without any doubt. Atheism is barely growing; one percent of Americans positively did not believe in God in 1965, two percent in 1991, and three percent in 2014.

Nor is disbelief fueling the trend toward no preference as beliefs changed much less during these years of institutional defection than between the 1960s to the 1990s when religious preferences changed little (and differential birth rates explained the changes that did occur).

It's risky to speculate, of course, but what seems to be happening is that theologically liberal protestantism has failed to maintain its hold on the hearts and minds of many of those it formerly counted among its number. As the doctrinal positions of the mainline churches were diluted to the point of insipidity people simply drifted away, taking their children with them.

Some of these found a home in more conservative churches with a more robust theology and others have simply become estranged from the church altogether. They've not become atheists, at least not in significant numbers, but they don't care to maintain an identification with any traditional religious body.