What if Christians keep leaving religion at the same rate observed in recent years? What if the pace of religious switching continues to accelerate? What if switching were to stop, but other demographic trends -- such as migration, births and deaths -- were to continue at current rates? To help answer such questions, Pew Research Center has modeled several hypothetical scenarios describing how the U.S. religious landscape might change over the next half century.

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%.1

Depending on whether religious switching continues at recent rates, speeds up or stops entirely, the projections show Christians of all ages shrinking from 64% to between a little more than half (54%) and just above one-third (35%) of all Americans by 2070. Over that same period, "nones" would rise from the current 30% to somewhere between 34% and 52% of the U.S. population.

What is religious switching?

The chart shows U.S. Christians projected to fall below 50% of population if recent trends continue.

However, these are not the only possibilities, and they are not meant as predictions of what will happen. Rather, this study presents formal demographic projections of what could happen under a few illustrative scenarios based on trends revealed by decades of survey data from Pew Research Center and the long-running General Social Survey.

All the projections start from the current religious composition of the U.S. population, taking account of religious differences by age and sex. Then, they factor in birth rates and migration patterns. Most importantly, they incorporate varying rates of religious switching -- movement into and out of broad categories of religious identity -- to model what the U.S. religious landscape would look like if switching stayed at its recent pace, continued to speed up (as it has been doing since the 1990s), or suddenly halted.

Switching rates are based on patterns observed in recent decades, through 2019. For example, we estimate that 31% of people raised Christian become unaffiliated between ages 15 to 29, the tumultuous period in which religious switching is concentrated.2 An additional 7% of people raised Christian become unaffiliated later in life, after the age of 30.

While the scenarios in this report vary in the extent of religious disaffiliation they project, they all show Christians continuing to shrink as a share of the U.S. population, even under the counterfactual assumption that all switching came to a complete stop in 2020. At the same time, the unaffiliated are projected to grow under all four scenarios.

Under each of the four scenarios, people of non-Christian religions would grow to represent 12%-13% of the population -- double their present share. This consistency does not imply more certainty or precision compared with projections for Christians and "nones." Rather, the growth of other religions is likely to hinge on the future of migration (rather than religious switching), and migration patterns are held constant across all four scenarios. (See Chapter 2 for an alternative scenario involving migration.)

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.

None of these hypothetical scenarios is certain to unfold exactly as modeled, but collectively they demonstrate how much impact switching could have on the overall population's religious composition within a few decades. The four main scenarios, combined with four alternatives outlined in Chapter 2, show that rates of religious switching in adulthood appear to have a far greater impact on the overall religious composition of the United States than other factors that can drive changes in affiliation over time, such as fertility rates and intergenerational transmission (i.e., how many parents pass their religion to their children).

The decline of Christianity and the rise of the "nones" may have complex causes and far-reaching consequences for politics, family life and civil society. However, theories about the root causes of religious change and speculation about its societal impact are not the focus of this report. The main contribution of this study is to analyze recent trends and show how the U.S. religious landscape would shift if they continued.

Why non-Christian religions are not projected individually
Scenario assumptions and projection results

The four main scenarios presented here vary primarily in their assumptions about the future of religious switching among Americans between the ages of 15 and 29 -- which are the years when most religious change happens. Only a modest amount of switching is modeled among older adults.

Fertility and mortality rates are held steady, as are rates of intergenerational transmission. In each scenario, the groups begin with their current profiles in terms of age and gender. Christians, for example, are older than the religiously unaffiliated, on average, and include a higher share of women.

Finally, the models assume that migration remains constant, which helps explain why non-Christian groups follow the same trajectory in each of the four scenarios. 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.

Chapter 2 presents four additional scenarios that explore the impact of the factors held constant here. These additional projections show how the U.S. religious landscape might change if current switching patterns held steady, but intergenerational religious transmission occurred in 100% of cases; there were no fertility differences by religion; there was no switching after age 30; or there was no migration after 2020.

The alternative scenarios are intended to help isolate -- and thereby illuminate -- the impact of various factors. One might think of the projections as an experiment in which some key drivers of religious composition change are turned on or off, sped up or slowed down, to see how much difference they make. For more information about modeling assumptions and results, see Chapter 2 and the Methodology.

For more click here: https://www.pewresearch.org/religion/2022/09/13/modeling-the-future-of-religion-in-america/: