Researchers can tell one thing from the data, though: People may be more willing to tolerate religious differences in their relationships than they have in the past—or they may be less willing to change their faiths for a romantic partner. Since the years leading up to 1960, when an estimated 81 percent of people married someone of their own faith, the number of “interfaith” unions has been creeping steadily upward. Among those who took their vows within the last half decade, only 61 percent married someone who shared their religion. The most common “interfaith” pairing was between Christians and people without religious affiliations; these couples accounted for 18 percent of those married after 2010. Again: Not everyone in America is ditching religion, but people are finding more and more flexibility in the institutions that once reinforced steady religious practice, like marriage.
Predictably, much of this movement in religious belief and practice has been happening among Millennials. More than a third of those aged 18 to 33 are religiously unaffiliated, and that proportion is even greater for the younger half of that cohort. Yet the researchers make it clear that changes in American religion are happening across demographic groups. “While the drop in Christian affiliation is particularly pronounced among young adults, it is occurring among Americans of all ages,” they write. “The same trends are seen among whites, blacks and Latinos; among both college graduates and adults with only a high-school education; and among women as well as men.”
This may make it sound like Christianity has entered a tailspin, but given its continued prominence in American life, that’s probably overdramatic. America is still a Christian nation, just by a somewhat smaller margin. Seven years ago, roughly 78 percent of the country was Christian. Now, that portion is closer to 71 percent, researchers estimate.
The U.S. is also proportionally more evangelical than it has been in the past. Researchers have known for a while that mainline denominations—including many Presbyterian, Methodist, Lutheran, and Episcopalian churches, along with a number of other groups—are losing members, and that’s starkly evident here. Over the past seven years, the percentage of Americans who identify with mainline churches has gone from 18.1 percent to 14.7 percent.
These denominations are getting older, too. The median age in mainline traditions is now 52, two years older than the median age in 2007. Catholicism faces similar challenges; the Church now accounts for 20.8 percent of Americans, compared to 23.9 percent seven years ago. Although some evangelical denominations are seeing more modest versions of the same trend—the portion of born-again Baptists in the U.S. population, for example, has declined by nearly 2 percentage points—by and large, these groups are holding steady in their membership. As a result, they account for a bigger share of American Christianity, and particularly of American Protestantism.