by Ryan Burge, Christianity Today, 3/21/19.
… As Tobin Grant, editor of the Journal for the Scientific Study of Religion, pointed out: “Changes in religion are slow. No group gains or loses quickly.” (The “nones,” a popular term for the religiously unaffiliated, being an exception—gaining faster than other affiliations tend to because they pull from multiple faith groups.)
That’s mostly what the 2018 GSS results show us. Evangelicals—grouped in this survey by church affiliation—continue to make up around 22.5 percent of the population as they have for much of the past decade, while the nones, now up to 23.1 percent themselves, keep growing. (For comparison, the Pew Research Center’s 2014 Religious Landscape Survey put evangelicals at 25.4 percent and the religious nones at 22.8 percent.)
Other than one outlier—a slight peak of 24.7 percent in 2012—evangelicals have ranged from 22.5 percent to 24 percent of the US population over the past 10 years. Still, this steadiness doesn’t mean “no change” among the evangelical population. There is always a “churn” occurring within any religious group. People leave the group because of death or defection, while new members either grow up in the faith or convert as adults.