The ARIS (American Religious Identification Survey) time series tracks changes in the religious loyalties of the American public. It comprises a set of three large replicate, representative, national surveys of adults in the continental U.S.A. (48 states & DC) in 1990, 2001 and 2008.  They have a common and consistent research design and methodology using random digit dialed telephone  interviews, and the same unprompted, open-ended key question: What is your religion, if any?  The value of this unique series of national surveys, which allows scientific monitoring of change over time, has been recognized by the U.S. Bureau of Census. The Census Bureau itself is  constitutionally precluded from such an inquiry into religion, and so has incorporated NSRI/ARIS findings into its own official publication the Statistical Abstract of the United States since 2003.

U.S. Census Bureau, Statistical Abstract of the United States: 2011

ARIS 2008 is the third in this landmark series of large, nationally representative surveys of U.S. adults in the 48 contiguous states conducted by Kosmin and Ariela Keysar. With a sample of over 50,000 respondents, ARIS is the largest national survey on American religion and it is the source cited by most media outlets for religious affiliation of Americans.