Americans' membership in houses of worship has continued to decline, dropping below 50% for the first time in Gallup's eight decades of tracking such membership. In 2020, only 47% of Americans said they belonged to a church, synagogue or mosque, down from 50% in 2018 and 70% in 1999.

By contrast, U.S. church membership was 73% when Gallup first measured it in 1937. It remained near 70% for the next six decades.

The decline in church membership coincides with the rise of the so-called “Nones” — those who claim no religious affiliation. Gallup reports about one in five Americans (21%) is a None — making them as large a group as evangelicals or Catholics.

Thus the membership decline is primarily a function of the increasing number of Americans who express no religious preference, according to the Gallup report released March 29, 2021. 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.

Most of the rest of the drop can be attributed to a decline in formal church membership among Americans who do have a religious preference. Between 1998 and 2000, an average of 73% of religious Americans belonged to a church, synagogue or mosque. Over the past three years, the average has fallen to 60%.

The decline in church membership 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. Currently, 31% of millennials have no religious affiliation, which is up from 22% a decade ago. Similarly, 33% of the portion of Generation Z that has reached adulthood have no religious preference.

the decline in membership is steeper among Catholics (down 18 points, from 76% to 58%) than Protestants (down 9 points, from 73% to 64%). In addition to Protestants, declines in church membership are proportionately smaller among political conservatives, Republicans, married adults and college graduates. These groups tend to have among the highest rates of church membership, along with Southern residents and non-Hispanic Black adults.

The U.S. remains a religious nation, with more than seven in 10 affiliating with some type of organized religion, according to other Gallup research. However, far fewer, now less than half, have a formal membership with a specific house of worship. As a Religion News Service analysis summarized, “Ask Americans if they believe in God and most will say yes. But a growing number have lost faith in organized religion.”