Organized religion will all but vanish eventually from nine Western-style democracies, a team of mathematicians predict in a new paper based on census data stretching back 100 years.
It won't die out completely, but "religion will be driven toward extinction" in countries including Ireland, Canada, Australia, New Zealand and the Netherlands, they say.
It will also wither away in Austria, the Czech Republic, Finland and Switzerland, they anticipate.
They can't make a prediction about the United States because the U.S. census doesn't ask about religion, lead author Daniel Abrams told CNN.
But nine other countries provide enough data for detailed mathematical modeling, he said.
"If you look at the data, 'unaffiliated' is the fastest-growing group" in those countries, he said.
"We start with two big assumptions based on sociology," he explained.
The first is that it's more attractive to be part of the majority than the minority, so as religious affiliation declines, it becomes more popular not to be a churchgoer than to be one, he said - what Abrams calls the majority effect.
"People are more likely to switch to groups with more members," he said.
Social networks can have a powerful influence, he said.
"Just a few connections to people who are (religiously) unaffiliated is enough to drive the effect," he said.
The other assumption underlying the prediction is that there are social, economic and political advantages to being unaffiliated with a religion in the countries where it's in decline - what Abrams calls the utility effect.
"The utility of being unaffiliated seems to be higher than affiliated in Western democracies," he said.
Abrams and his co-authors are not passing any judgment on religion, he's quick to say - they're just modeling a prediction based on trends.
"We're not trying to make any commentary about religion or whether people should be religious or not," he said.
"I became interested in this because I saw survey data results for the U.S. and was surprised by how large the unaffiliated group was," he said, referring to a number of studies done by universities and think tanks on trends in religion.
Studies suggest that "unaffiliated" is the fastest-growing religious group in the United States, with about 15% of the population falling into a category experts call the "nones."
They're not necessarily atheists or non-believers, experts say, just people who do not associate themselves with a particular religion or house of worship at the time of the survey.
Abrams had done an earlier study looking into the extinction of languages spoken by small numbers of people.
When he saw the religion data, his co-author "Richard Wiener suggested we try to apply a similar technique to religious affiliation," Abrams said.
The paper, by Abrams, Wiener and Haley A. Yaple, is called "A mathematical model of social group competition with application to the growth of religious non-affiliation." They presented it this week at the Dallas meeting of the American Physical Society.
Only the Czech Republic already has a majority of people who are unaffiliated with religion, but the Netherlands, for example, will go from about 40% unaffiliated today to more than 70% by 2050, they expect.
Even deeply Catholic Ireland will see religion die out, the model predicts.
"They've gone from 0.04% unaffiliated in 1961 to 4.2% in 2006, our most recent data point," Abrams says.
He admits that the increase in Muslim immigration to Europe may throw off the model, but he thinks the trend is robust enough to withstand some challenges.
"Netherlands data goes back to 1860," he pointed out. "Every single data that we were able to find shows that people are moving from the affiliated to unaffiliated. I can't imagine that will change, but that's personal opinion, not what the data shows."
But Barry Kosmin, a demographer of religion at Trinity College in Connecticut, is doubtful.
"Religion relies on human beings. They aren't rational or predictable according to the laws of physics. Religious fervor waxes and wanes in unpredictable ways," he said.
"The Jewish tradition that says prophecy is for fools and children is probably wise," he added.
And Abrams, Wiener and Yaple are not the first to predict the end of religion.
Peter Berger, a former president of the Society for the Scientific Study of Religion, once said that, "People will become so bored with what religious groups have to offer that they will look elsewhere."
He said Protestantism "has reached the strange state of self-liquidation," that Catholicism was in severe crisis, and anticipated that "religions are likely to survive in small enclaves and pockets" in the United States.
He made those predictions in February 1968.