Pew Research Center · Princeton Survey Research Associates International (PSRAI)
The first Religious Landscape Survey: 35,556 adults in the continental U.S., interviewed by telephone in summer 2007, plus a supplemental spring 2008 sample of 200 Alaska and 201 Hawaii adults (reported separately; the two files don't share a combining weight). This is the survey that first measured the scale of religious switching in America and established the RELTRAD religious-tradition classification later waves (2014, 2023-24) still use.