How Many Atheists Are In The United States ?

Some people like to think the United States is a christian country. While it's true that a substantial majority of Americans claim to be christians, no one branch of christianity (evangelicals, catholics, mainstream protestants, etc.) makes up anywhere near a majority -- and each year a larger percentage claim to be not religious.
The chart above comes from a recent Gallup Poll. They asked respondents if there was a god or not, and 12% of the population said there was no god. That is undoubtably an undercount. There are people who do not believe god exists (which is the definition of an atheist), but won't admit it because they live in a religious family, neighborhood, city, or state -- and don't want the harassment they feel would come with the atheist label.

The following article in Scientific American,  Michael Shermer tries to answer that question. Here is part of that article:

In a paper in the January 2018 issue of the journal Social Psychological and Personality Scienceentitled “How Many Atheists Are There?”, Will M. Gervais and Maxine B. Najle, both psychologists at the University of Kentucky, contend that there may be far more atheists than pollsters report because “social pressures favoring religiosity, coupled with stigma against religious disbelief..., might cause people who privately disbelieve in God to nonetheless self-present as believers, even in anonymous questionnaires.”

To work around this problem of self-reported data, the psychologists employed what is called an unmatched count technique, which has been previously validated for estimating the size of other underreported cohorts, such as the LGBTQ community. They contracted with YouGov to conduct two surveys of 2,000 American adults each, for a total of 4,000 subjects, asking participants to indicate how many innocuous versus sensitive statements on a list were true for them. The researchers then applied a Bayesian probability estimation to compare their results with similar Gallup and Pew polls of 2,000 American adults each. From this analysis, they estimated, with 93 percent certainty, that somewhere between 17 and 35 percent of Americans are atheists, with a “most credible indirect estimate” of 26 percent. If true, this means that there are more than 64 million American atheists, a staggering number that no politician can afford to ignore. Moreover, if these trends continue, we should be thinking about the deeper implications for how people will find meaning as the traditional source of it wanes in influence. And we should continue working on grounding our morals and values on viable secular sources such as reason and science.