Here’s a simple question: How many Americans don’t believe in God?

Pew and Gallup — two of the most reputable polling firms in America — both come to a similar figure. About 10 percent of Americans say they do not believe in God, and this figure has been slowly creeping up over the decades.

But maybe this isn’t the whole story. University of Kentucky psychologists Will Gervais and Maxine Najle have long suspected that a lot of atheists aren’t showing up in these polls. The reason: Even in our increasingly secular society, there’s still a lot of stigma around not believing in God. So when a stranger conducting a poll calls and asks the question, it may be uncomfortable for many to answer truthfully.

Gervais and Najle recently conducted a new analysis on the prevalence of atheists in America. And they conclude the number of people who do not believe in God may be even double that counted by these polling firms.

“There’s a lot of atheists in the closet,” Gervais says. “And ... if they knew there are lots of people just like them out there, that could potentially promote more tolerance.”

People are embarrassed to tell strangers they don’t believe in God

Currently, if you’re seeking data to answer the question, “How many Americans do not believe in God?” you have two main sources.

First is the Pew Research Center. Most recently, Pew found that around 3 percent of Americans say they are atheists. It also found that a larger group — around 9 percent — say they do not believe in God or a universal spirit. (Which goes to show that you may not believe in God but could still be uncomfortable calling yourself an atheist — because that term implies a strong personal identity and an outright rejection of religious rituals.) Gallup also regularly asks the question point blank — “Do you believe in God?” The last time it asked, in 2016, 10 percent of respondents said no.

Gervais’s experience studying the stigma around atheism the world over made him suspect these numbers are wrong.

Study after study has shown that most people (even other atheists) believe atheists are less moral. “We’ll give participants a little vignette, a story about someone doing something immoral, and probe their intuition about who they think the perpetrator was,” Gervais says. “And time and time again, people intuitively assume whoever is out there doing immoral stuff doesn’t believe in God.”

So it would make sense that when Pew or Gallup calls, people who don’t believe in God may be reluctant to say so. “We shouldn’t expect people to give a stranger over the phone an honest answer to that question,” Gervais says.

So recently, Gervais and Najle designed a test to find these “closet atheists.” Their results were recently published in the journal Social Psychological and Personality Science.

How to find “closet atheists”

So if you can’t ask people outright whether they’re atheist and get an honest response, how do you go about finding them?

Gervais and Najle set up a very subtle test. They sent a nationally representative poll to 2,000 Americans, who were randomly assigned to two conditions.

The first condition asked participants to read through a bunch of statements like, “I am a vegetarian,” “I own a dog,” and, “I have a dishwasher in my kitchen.”

All the participants had to do was simply write down the number of statements that were true for them.

The value of this method is that participants don’t have to directly say, “I am a vegetarian,” or, “I’m a dog owner” — they only have to acknowledge the number of statements that apply to them. That alone should zero out any embarrassment or hesitance to admit to a particular item.

That’s important because the other 1,000 or so participants saw the exact same list — but with one statement added: “I believe in God.”

By comparing the responses between the two groups, Gervais and Najle could then estimate how many people don’t believe in God. (Because both groups of 1,000 poll takers should, in theory, have the same number of vegetarians, dog owners, and so on in each group, any increases in the number of agreed-to statements from the first group to the second should be reflective of the number of people who don’t believe in God.)

One thing is clear from the results: Much more than 10 or 11 percent of the country (as assessed in Gallup and Pew polling) does not believe in God. “We can say with a 99 percent probability that it’s higher than [11 percent],” said Gervais.

His best estimate: Around 26 percent of Americans don’t believe in God. “According to our samples, about 1 in 3 atheists in our country don't feel comfortable disclosing their lack of belief,” Najle explains in an email.

Gervais admits this method isn’t perfect, and yields an answer with a wide margin of error. (On the other end of the margin of error, around 35 percent of Americans don’t believe in God.) But the most fundamental question he and Najle are asking here is do polling firms like Gallup and Pew undercount atheists? And it seems the answer is yes.

Gervais and Najle also concurrently replicated the study with a second sample of 2,000 participants, and got similar results. (In this second sample, they framed the atheism question in the negative — “I do not believe in God” — which yielded a slightly lower number of atheists. This could be because people are a bit more anxious to respond to such a definite phrase as, “No, I do not believe in God.”)

Could this really be true? A few grains of salt.

I ran Gervais and Najle’s conclusion by Greg Smith, who directs Pew’s polling efforts on religion. He’s not yet ready to buy it.

“I would be very reluctant to conclude that phone surveys like ours are underestimating the share the public who are atheists to that kind of magnitude,” he says.

For one, Smith says, Pew has asked questions on religion both on the phone and online and didn’t see much of a difference. You’d expect if people were unwilling to say that they’re atheists over the phone to a stranger, they’d be slightly more likely to input it into a computer. (Though Pew’s online questioning still has participants directly answer the question, instead of asking people to merely list the numbers of items they agree with. Even online, people might be uneasy answering the question.)

Also, Smith points out a weird quirk in Gervais’s data.

In one of the trials, instead of adding the “I don’t believe in God” measure to the list, the survey added a nonsense phrase: “I do not believe that 2 + 2 is less than 13.” And 34 percent of their participants agreed. Bizarre indeed. The researchers’ explanation? “It may reflect any combination of genuine innumeracy [lack of math skills], incomprehension of an oddly phrased item, participant inattentiveness or jesting, sampling error, or a genuine flaw in the ... technique,” Gervais and Najle write in the paper.

But they still think their measure is valid. When they limited the sample to people who were self-professed atheists (as measured in a separate question), 100 percent said they didn’t believe in God, which is correct. “It is unlikely that a genuinely invalid method would track self-reported atheism this precisely,” they write.

Still, more research is needed. “In time, we'll hopefully be able to refine our methods and find other indirect measurement techniques,” Gervais says. (Overall, kudos to Gervais and Najle for being forthright about their curious finding. In the past, psychologists have had incentives to avoid printing this type of contradictory finding in their papers.)

For a lot of us, belief in God is not a binary

There’s something else to consider here: Our experience with religion can’t really be boiled down to one question — “Do you believe in God?”

Many of us have a complicated relationship with religion. There are plenty of people celebrating Easter and Passover this week not because they have devout faith, but because it’s a cultural tradition they cherish and identify with.

Pew regularly finds data that supports this multifaceted view. When people in their surveys say, “I believe in God,” Pew will often ask a follow-up question: “How certain are you?” And they find that not everyone is so sure.

About a quarter of the US population say they believe in God but are less than absolutely certain of it, Smith says.

The lesson: Belief in God doesn’t exist as a binary. Not everyone is certain about what they feel; many people have shades of gray. “There are gradations of belief,” Smith says. “It’s not that it’s wrong to ask ‘yes or no,’ but it’s not the whole story.”

And Gervais admits: This measure doesn’t capture the complex and contradictory feelings many people have about religion. (And Najle adds that these data “are limited to the U.S. and should not be generalized beyond that.”)

But in the data, they also find some small evidence that the stigma around atheism is changing. When they break the numbers down by demographics, they find that baby boomer and millennials report similar levels of disbelief (even though traditional polling shows baby boomers are more likely to believe in god). This could be because younger people feel less anxious about their atheism.

“It could be underlying belief levels haven’t changed,” Gervais says, comparing the generations, “but norms have.”