The percentage of Americans who consider themselves Christian may fall from 64 percent to under 50 percent by 2070 if current trends continue, according to a new Pew Research Center report. The percentage of people who describe themselves as atheist, agnostic or "nothing in particular" may also top 40 percent, the report found.

The report, Modeling the Future of Religion in America, combines decades of Pew data with data from the General Social Survey to present four hypothetical models of the future of faith in the U.S.

Pew estimates that in 2020, 64 percent of all Americans (including children) were Christian.

Yet, in all four models, that percentage will shrink. In fact, in three of the four models, the number falls below 50 percent. (Pew's four models have Christianity falling to either 54 percent, 46 percent, 39 percent or 35 percent.)

Meanwhile, the percentage of the much-discussed "nones" - those who consider themselves atheist, agnostic or "nothing in particular" - will rise from the current 30 percent to either 34 percent, 41 percent, 48 percent or 52 percent by 2070, according to Pew's models.

The report notes that all the models are hypothetical. The differences depend on whether religious switching "continues at recent rates, speeds up or stops entirely," the report said.

"All the projections start from the current religious composition of the U.S. population, taking account of religious differences by age and sex," the report said. 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."

The models are "not meant as predictions of what will happen," it said. World events, the report added, could have a dramatic impact on religious trends.

"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," Pew said. "But there are no current switching patterns in the U.S. that can be factored into the mathematical models to project such a result."