Millennials — those between ages 23 and 48 — are shaking up the workplace, transforming dating and undoing organized religion.

Four in 10 American millennials now describe themselves as religiously unaffiliated, according to the Pew Research Center, which notes that those in the age group are almost as likely to say they have no religion as they are to identify as Christian.

That is a higher percentage than the estimated 25 percent of Americans of all ages who do not identify with any religion, according to a previous Pew study.

And there’s mounting evidence that the younger adults in the millennial generation are leaving religion for good.

At this point, a large proportion of millennials have spouses, children and mortgages — and there’s little evidence that religious interest has re-emerged.

A new national survey from theAmerican Enterprise Institute of more than 2,500 Americans found a few reasons that millennials are not returning to the religious fold.

Those who never had strong ties to religion to begin with have not developed habits or associations that make it easier to return to a religious community.

Younger adults also are increasingly likely to have a spouse who is nonreligious.

Morality and religion are less connected for millennial parents, with those who are unaffiliated finding religious institutions irrelevant or unnecessary for their children to learn ethics.

Millennials may be leading a societal shift away from religion, but they didn’t start it on their own. Their parents are at least partly responsible.

According to the AEI survey, 17 percent of millennials said they were not raised in any particular religion compared with only 5 percent of baby boomers. Only one-third of millennials said they attended weekly religious services with their family when they were young, compared with about half of their parents’ generation.

A parent’s religious identity —or lack thereof—can do a lot to shape a child’s religious habits and beliefs later in life. A 2016 Pew Research Center study found that regardless of the religion, those raised in households in which both parents shared the same religion still identified with that faith in adulthood.

For instance, 84 percent of people raised by Protestant parents are still Protestant as adults. That same Pew study found that 63 percent of people who grew up with two religiously unaffiliated parents were still nonreligious as adults.

One finding in the recent AEI survey signals that millennials who grew up religious may be increasingly unlikely to return to organized worship. In the 1970s, most nonreligious Americans had a religious spouse and often that partner would draw them back into regular religious practice.

But a growing number of unaffiliated Americans are settling down with someone who isn’t religious. Today, 74 percent of unaffiliated millennials have a nonreligious partner or spouse, while only 26 percent have a partner who is religious.

Among unaffiliated millennials, those who are religious are seen as having a narrower view of humanity and of right and wrong. The AEI survey found that 57 percent of millennials agreed with the statement that religious people are generally less tolerant of others, compared to only 37 percent of baby boomers.

The poll also found only 46 percent of millennials agreed that it is necessary to believe in God to be moral. While 75 percent of baby boomers agreed that it is important for children to be brought up in a religion so they can learn good values, only 57 percent of millennials agreed. That impacts church attendance.

In the AEI survey, less than half of millennial parents stated they regularly take their children to a religious service and less than 40 percent ensure their children get religious instruction through Sunday School or other religious education program, a drop of 20 percentage points from polls of baby boomers.

Of course, millennials’ religious trajectory isn’t set in stone. They may yet become more religious as they age.

But it’s easier to return to something familiar later in life than to try something completely new.

And if those unaffiliated millennials don’t return to religion and raise a new generation with no religious background, the gulf between religious and secular America will only widen.