It’s tough to figure out just how religious or nonreligious different populations of people are. Widely-cited telephone polls (e.g., Gallup, Pew) suggest U.S. atheist prevalence ranging from 3% to 11%. But in the US, there’s heavy stigma leveled against religious disbelief, which might make people reluctant to disclose their lack of belief over the phone to a stranger. Using a subtle, indirect measurement technique, psychology researchers have found that atheists may represent anywhere from 20% to 35% of the U.S. population.