Modeling the decline of American Christianity

What does America look like if the decline in Christian belief continues? What might this mean for higher education?

I’ve been tracking this religious trend for a while (2021, 2019, 2017). Today I’d like to follow up with a new Pew study, which models several possible scenarios for American religious transformation.  As a futurist who tracks religion, but is not a religion scholar, I found the work fascinating and useful.  It’s a good example of evidence-based trend analysis, extrapolation, and scenario development.

The main focus of the study (Stephanie Kramer et al) is people switching religions. In the American context, or in the view of Pew, this means a person being born in a Christian faith, then leaving for something else, including to a status of no formal religious affiliation.  “Since the 1990s, large numbers of Americans have left Christianity to join the growing ranks of U.S. adults who describe their religious identity as atheist, agnostic or ‘nothing in particular.’”

The report starts from a 2020 baseline, then extrapolates several scenarios based on different forms the decline trend might take.  That baseline looks like this:

The Center estimates that in 2020, about 64% of Americans, including children, were Christian. People who are religiously unaffiliated, sometimes called religious “nones,” accounted for 30% of the U.S. population. Adherents of all other religions – including Jews, Muslims, Hindus and Buddhists – totaled about 6%.

From that baseline, how might America change if the observed dis-Christianization continues?  To explore this, Pew offers several models of Christian affiliation in decline, depending on how the trend plays out:

American religious affiliation 1970-2070_Pew

You can see different dates when Christian affiliation falls below one half of the population, unless the “no switching” change occurs.

At the same time, the proportion of “nones” (“People who are religiously unaffiliated”) rises to different levels, again depending on how that trend takes shape:

American religious affiliation by nones -1972-2070_Pew

At the same time that 6%, those who are neither Christian nor “none,” will likely grow.  “Under each of the four scenarios, people of non-Christian religions would grow to represent 12%-13% of the population – double their present share.”  Interestingly, Pew sees this driven not by switching, but largely by migration:

Immigration has an outsized effect on the composition of non-Christian groups in the U.S. because adherents of religions like Islam and Hinduism make up a larger share of new arrivals than they do of the existing U.S. population.

The report wraps these three projection sets together to create four different scenarios, which are too short for me to summarize usefully, so I’ll just share them directly:

Scenario 1: Steady switching – Christians would lose their majority but would still be the largest U.S. religious group in 2070

Switching assumption: Switching into and out of Christianity, other religions and the religiously unaffiliated category (“nones”) continues among young Americans (ages 15 to 29) at the same rates as in recent years. Most significantly, each new generation sees 31% of people who were raised Christian become religiously unaffiliated by the time they reach 30, while 21% of those who grew up with no religion become Christian.

Outcome: If switching among young Americans continued at recent rates, Christians would decline as a share of the population by a few percentage points per decade, dipping below 50% by 2060. In 2070, 46% of Americans would identify as Christian, making Christianity a plurality – the most common religious identity – but no longer a majority. In this scenario, the share of “nones” would not climb above 41% by 2070.

American religious affiliation 1970-2070_Pew scenario 1

In contrast, a world with more “nones” and fewer Christians:

Scenario 2: Rising disaffiliation with limits – ‘nones’ would be the largest group in 2070 but not a majority

Switching assumption: Continuing a recent pattern, switching out of Christianity becomes more common among young Americans as each generation sees a progressively larger share of Christians leave religion by the age of 30. However, brakes are applied to keep Christian retention (the share of people raised as Christians who remain Christian) from falling below about 50%.3 At the same time, switching into Christianity becomes less and less common, also continuing recent trends.

Outcome: If the pace of switching before the age of 30 were to speed up initially but then hold steady, Christians would lose their majority status by 2050, when they would be 47% of the U.S. population (versus 42% for the unaffiliated). In 2070, “nones” would constitute a plurality of 48%, and Christians would account for 39% of Americans.

American religious affiliation 1970-2070_Pew scenario 2

Pushing things a bit further, a new majority appears:

Scenario 3: Rising disaffiliation without limits – ‘nones’ would form a slim majority in 2070

Switching assumption: The share of Christians who disaffiliate by the time they reach 30 continues to rise with each successive generation, and rates of disaffiliation are allowed to continue rising even after Christian retention drops below 50% (i.e., no limit is imposed). As in Scenario 2, switching into Christianity among young Americans becomes less and less common.

Outcome: If the pace of switching before the age of 30 were to speed up throughout the projection period without any brakes, Christians would no longer be a majority by 2045. By 2055, the unaffiliated would make up the largest group (46%), ahead of Christians (43%). In 2070, 52% of Americans would be unaffiliated, while a little more than a third (35%) would be Christian.

American religious affiliation 1970-2070_Pew scenario 3

Or if switching away from Christianity slows down in a big way:

Scenario 4: No switching – Christians would retain their majority through 2070

Switching assumption: This scenario imagines no person in America has changed or will change their religion after 2020. But even in that hypothetical situation, the religious makeup of the U.S. population would continue to shift gradually, primarily as a result of Christians being older than other groups, on average, and the unaffiliated being younger, with a larger share of their population of childbearing age.

Outcome: If switching had stopped altogether in 2020, the share of Christians would still decline by 10 percentage points over 50 years, reaching 54% in 2070. The unaffiliated would remain a substantial minority, at 34%.

American religious affiliation 1970-2070_Pew scenario 4

To the authors’ credit, they offer four more scenarios, based on changing various inputs to their model:

American religious affiliation 1970-2070_Pew scenarios 5-8

All told, those scenarios take us to 2070, roughly.  The report then ventures a generation ahead, too, and suggests a change in this disaffiliation/rising none trend:

If trends are projected for an even longer period, change slows under most scenarios. Even in the most extreme switching scenario, in which each cohort of young adults disaffiliates more than the one before it, with no floor imposed for Christian retention, Christians would still represent about a quarter of the population in 2100. Under other scenarios, the rate of growth of the religiously unaffiliated (and decline of Christians) is curbed by 2080. This is due to switching dynamics. If the Christian and unaffiliated populations become similar in size – an eventuality under most scenarios – and if the gap between their retention rates remains small, then the growth of the unaffiliated eventually would slow, and the religious groups could reach equilibrium rather than one group ascending completely and the other disappearing.

Note that the report hedges its forecasts carefully.  For example,

Of course, it is possible that events outside the study’s model – such as war, economic depression, climate crisis, changing immigration patterns or religious innovations – could reverse current religious switching trends, leading to a revival of Christianity in the United States. But there are no current switching patterns in the U.S. that can be factored into the mathematical models to project such a result.

I would add the enormous possibilities opened up by swelling numbers of “nones.”  Consider how the report describes that population:

[R]eligiously unaffiliated Americans today are not uniformly nonbelieving or nonpracticing. Many religious “nones” partake in traditional religious practices despite their lack of religious identity, including a solid majority who believe in some kind of higher power or spiritual force. It is also unclear how this may change in the future, and whether connections to these beliefs will weaken if disaffiliation becomes even more common in the broader society. At the same time, many observers have wondered what kinds of spiritual practices, if any, may fill the void left by institutional religion. We plan to continue exploring this question in future research.

We could easily see a swath of that group heading to a new religion (again, I’ve been monitoring new religious movements for this and other reasons) or to an established one that has become appealing due to changes in message, leadership, practices, etc.

What might this mean for colleges and universities?

There are several potential impacts, as I’ve pointed out previously.

  1. Declining Christian affiliation threatens religious colleges and universities in their enrollment, staffing, alumni connections, and overall relevance.  This can lead to institutional cuts, program and department closures, campuses shut down, or mergers.
  2. A number of American colleges and universities have formal religious identities. Would their leaders feel impelled to change this status?
  3. Religious studies as a field of research and teaching may similarly be constrained, if interest follows religious affiliation.  We’ve seen evidence of that in plummeting numbers of majors. Imagine how religious classes within a general curriculum might suffer, or change in order to win students.
  4. Intergenerational tension might heighten. That would be due to a belief or religious membership gap opening up between the youngest and older people belonging to a college or university.
  5. A variation of #3: supporting students may become more challenging, depending on the context.  I imagine older faculty and staff with religious beliefs helping increasingly irreligious students succeed, and the possibility of clashes there. The opposite could also occur, as the number of older students grows while younger people increasingly become staff and faculty.
  6. Animosity towards education, particularly from the right, may take on a more deeply religious cast, to the extent that partisans link unbelief with higher ed remain.  It’s not much of a stretch to imagine Republicans deeply critical of universities and fearful of Godlessness combining the two more closely.

One more implication, newly emerged, is that this changing religious landscape intersects with the end of Roe v Wade.  I wrote in June about how local abortion rules might impact colleges and universities. Perhaps we’ll see religious affiliation become more geographically sorted, with “nones” leaving states with strong abortion restrictions and some of the Christian population moving to them.

Let me add some caveats of my own, in addition to those offered by the Pew report.  I’m still open to the possibility of a major new religion appearing in this century, perhaps anchored on the climate crisis, and that could engage a great deal of “nones.”  We have also seen various New Age and generally “spiritual” figures and groups appear since the 1960s; those could coalesce into something more institutional.

Further, these are national trends and scenarios.  For a large, diverse, and complex society like America, there are all kinds of local variations to play out.  As we saw in 2017, religious affiliation varies strongly by race, gender, education, sexuality, and geography, among other factors.


The full report covers a lot of ground, including different ages and their religious behavior, intergenerational transmission, migration, and issues with different dataset.  I recommend the whole thing to you, and would like to hear people’s thoughts and reactions.

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3 Responses to Modeling the decline of American Christianity

  1. Trent Batson says:

    Bryan: religion in society — the topic of my PhD dissertation — is one way to understand culture, as you are suggesting. I’ll just make one comment: Georgetown is a Jesuit institution, as you well know, and in its environmental offerings is using St. Francis as a model. To me, this is a brilliant and almost obvious fusion of belief, humility and intelligence for the purpose of dealing with climate change. Other denominations are similarly looking for bases in belief to increase consciousness of the human responsibility for good stewardship. The trends you point to are of course accurate, but amidst those demographic trends, we may be seeing a re-forming of religious thought for these times.

  2. Glen McGhee says:

    Thank you for your thoughtful analysis, which raises the question about Covid and how Covid has impacted the organizational church — and to what role extant formal organizations play in the maintenance of belief structures.
    Pew does not explore this cognitive nexus, which is plausibly causal.
    Thank you again!

  3. Dahn Shaulis says:

    Bryan, there are so many strange contradictions with the US and its religions. While Christianity may currently be in decline, Christian Authoritarianism has been gaining greater political power in the US and other nations. And the 7 Mountains Theology, an effort to dominate all aspects of culture, is one of the main ideas within Christian Authoritarianism. This movement should not be underestimated and may be the fuel for greater internal conflict.

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