*The following is excerpted from an online article posted on Gallup News.
Americans' membership in houses of worship continued to decline last year, dropping below 50% for the first time in Gallup's eight-decade trend. In 2020, 47% of Americans said they belonged to a church, synagogue, or mosque, down from 50% in 2018 and 70% in 1999.
U.S. church membership was 73% when Gallup first measured it in 1937 and remained near 70% for the next six decades, before beginning a steady decline around the turn of the 21st century.
The decline in church membership is primarily a function of the increasing number of Americans who express no religious preference. Over the past two decades, the percentage of Americans who do not identify with any religion has grown from 8% in 1998-2000 to 13% in 2008-2010 and 21% over the past three years.
As would be expected, Americans without a religious preference are highly unlikely to belong to a church, synagogue, or mosque, although a small proportion -- 4% in the 2018-2020 data -- say they do. That figure is down from 10% between 1998 and 2000.
Given the nearly perfect alignment between not having a religious preference and not belonging to a church, the 13-percentage-point increase in no religious affiliation since 1998-2000 appears to account for more than half of the 20-point decline in church membership over the same time.
Church membership is strongly correlated with age, as 66% of traditionalists -- U.S. adults born before 1946 -- belong to a church, compared with 58% of baby boomers, 50% of those in Generation X, and 36% of millennials.
The decline in church membership, then, appears largely tied to population change, with those in older generations who were likely to be church members being replaced in the U.S. adult population with people in younger generations who are less likely to belong.
Among religious groups, the decline in membership is steeper among Catholics (down 18 points, from 76% to 58%) than Protestants (down nine points, from 73% to 64%).