The National Public Opinion Reference Survey (NPORS)

NPORS is an annual survey of U.S. adults conducted by Pew Research Center. Respondents can answer either by paper or online, and they are selected using address-based sampling from the USPS’s computerized delivery sequence file. Respondents are not required to join a survey panel. Pew Research Center uses NPORS to produce benchmark estimates for several topics, such as Americans’ political and religious affiliations