A recent Gallup poll suggests a drift from Protestant identity fueled the rise of religious “nones” in America.

In 1955, just 1 percent of young Americans aged 21 to 29 were religiously unaffiliated. That year, a majority (66 percent) identified as Protestant.

Today, only half as many young adults in their 20s identify as Protestant. And most of the migration has been toward the growing ranks of the religious “nones.” In fact, there are now as many “nones” as Protestants in this age group, with each group claiming 33 percent of 21- to 29-year-olds in the U.S.

Similar shifts are evident among older generations. The share of Protestants aged 30 to 39 fell 28 percentage points between 1955 and 2017, from 68 to 40 percent. Meanwhile, the percentage of “nones” jumped by nearly the same amount during that period, from 1 to 28 percent.

Gallup tracked a decline of 25 percentage points among Americans in their 40s; 22 percentage points among 50-somethings; and 23 percentage points among those 60 and older.

Among young adults in their 20s, there are now as many “nones” as Protestants.

Overall, Protestant affiliation in the U.S. fell from 71 percent in 1955 to just under half of Americans (47 percent) in 2017. Over those six decades, the percentage of Americans claiming no religious affiliation rose from 1 to 20 percent.

The share of those affiliating with Catholicism held steady, falling just 2 percentage points, from 24 percent in 1955 to 22 percent in 2017.

The percentage of Americans affiliating with other religions increased from 4 to 11 percent.

Those affiliating with the Catholic Church today are significantly less likely to attend services than Catholics in the 1950s (75 percent then vs. 39 percent now). That’s not the case with Protestants, however.

Despite the Protestant decline, those who do identify as Protestants today are just as likely to attend services as they were 62 years ago (42 percent then vs. 45 percent now).

It’s helpful to remember that the “none” movement didn’t emerge in a religious vacuum. Many of these unaffiliated adults are the children and grandchildren of Protestants. However, that doesn’t mean they have an understanding of the gospel.

In fact, half of Americans today either never read Scripture (27 percent) or don’t open a Bible more than once or twice a year (23 percent), according to Barna Group. Churches across America must find ways to reach this growing post-Christian demographic with the transforming message of Christ.