Pew Research, 9/13/22.
… 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.
… 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.