Inside the American Trends Panel: How Pew Builds Its Numbers

Pew Research Center's most cited numbers, the ones this atlas draws on for national and global religious composition, come from a single standing instrument called the American Trends Panel. Built from 2014 onward, the panel now holds roughly ten thousand adults recruited at random from across the United States, not volunteers who signed up on their own. Early recruitment used landline and cell phone random digit dialing; since 2018 the center has recruited by address based sampling instead, mailing an invitation and a small incentive to a random sample of households drawn from the Postal Service's own delivery file, which covers nearly the whole country. Panelists who agree to join answer self administered surveys online roughly once a month, in English or Spanish, and anyone without home internet access is given a tablet and a wireless connection rather than being dropped from the sample for lacking one. What began as a supplement to telephone polling has, as phone response rates fell and phone surveys grew more expensive to run, become the center's primary way of collecting data. Raw answers are not published as counted; every wave is weighted in several steps, starting from each panelist's own probability of having been selected at all and then calibrated against known population benchmarks to correct for the people who declined to join and the ones who drift away over time. That is the machinery behind the Religious Landscape Study and the Global Religious Landscape estimates this atlas cites again and again: not a single poll but a maintained panel, rebuilt from the sampling frame up, with its weighting and its coverage published alongside every release for anyone who wants to check the arithmetic themselves.