And church attendance by Roman Catholics is on the decline again. So, in fact, is the religious affiliation among Americans at large.

The drop continues a long trend of declining attendance at mass. In the last three years, an average of only 39 percent of Catholics reported attending church in the past week. That’s down from an average of 45 percent just 10 years ago. And severely off from the mid-1900’s. In 1955, for instance, 75 percent of Catholics reported attending mass during the previous week.

On the other side of the aisle, the new Gallup survey found that church attendance by Protestants is holding steady, although the population of Protestants overall has declined. The average weekly attendance was 45 percent these last three years, the same as 10 years ago.

And here’s a disturbing stunner: In 1955, Gallup found only two percent of the country claimed no religious identity. In 2016, the same survey found that proportion had grown 10 times, to 20 percent.

Back in 1955 about three-quarters of Catholics of all ages attended weekly mass. But in the 1960’s younger Catholics reported attending mass increasingly less often, a trend that accelerated through the 1970’s, then slowed but continued.

Older Catholics also began a trend of attending mass less often. In fact, in the last decade alone attendance has been dropping 10 percent among Catholics age 50 and older.

Church attendance by Protestants was never as high as Catholics. Protestant attendance did dip in the 1960’s and 1970’s but, unlike Catholics, has since rebounded. Indeed, among Protestants age 60 and over, attendance has actually increased eight points since the mid-fifties.

What’s changed among Protestants, however, is the percentage of Americans identifying with that faith has plummeted from 71 percent in 1955 to just 47 percent more recently. The percentage of Americans identifying as Catholic has held fairly steady at 24 percent now instead of 22 percent 60 years ago, in large part due to the explosion of the Hispanic population.

One troubling sign for the future spiritual and financial strength of both churches is Americans in their twenties attending services less frequently–Protestants 36 percent and Catholics 25 percent. And a growing proportion in that age cohort have stopped identifying with any religion, 33 percent.