Religious affiliation and faith community membership in the U.S. continue to decline, according to a Gallup report published April 18.

Over the last two decades, involvement in a church, mosque or synagogue has declined 20%, reaching an all-time low of 50% in 2018.

Religious affiliation has declined by 13 points to 77% over the same period, while those who don’t affiliate with a religious tradition have increased from 8% to 19%.

Fewer U.S. adults who still claim a religious tradition are involved in houses of faith.

From 2016 to 2018, an average of 64% of the religiously affiliated belonged to a church, mosque or synagogue – down nine points from an average of 73% from 1998 to 2000.

Younger generations are driving these trends, as they are more likely to be unaffiliated with a faith tradition and less likely to be involved in a local faith community.

For example, from 2016 to 2018, an average of 68% of adults born in 1945 or before were members of a church, mosque or synagogue (down from 77% in 1998 to 2000), compared to 42% of adults born from 1980 to 2000.

Similarly, those born between 1980 and 2000 were more than three times as likely to be unaffiliated as those born in 1945 or before.

Among Christian traditions, Catholics have seen the sharpest decline in church membership, dropping from 76% to 63% over the past 20 years, while Protestants have declined six points to 67%.

“There is an almost one-to-one correspondence between not being religious and not belonging to a church,” the report said. “Consequently, the 11-point increase in no religious affiliation accounts for the majority of the 17-point decline in church membership over the past two decades.”

The full report is available here.