This "is a growing collection of over 41,000 adherent statistics and religious geography citations -- references to published membership/adherent statistics and congregation statistics for over 4,200 religions, churches, denominations, religious bodies, faith groups, tribes, cultures, movements, ultimate concerns, etc." Data are from both primary research sources such as government census reports, statistical sampling surveys and organizational reporting, as well as citations from secondary literature which mention adherent statistics.
- American Religion Data Archive
This archive provides quantitative data on American religion. The ARDA collection includes data on churches and church membership, religious professionals, and religious groups (individuals, congregations and denominations).
- CIA World Factbook
This publication, updated yearly, by the Central Intelligence Agency (CIA) gives an ordered listing of religions by adherents starting with the largest group and sometimes includes the percent of total population.
- International Religious Freedom Report
Submitted to the Congress by the Department of State. Supplements the most recent Human Rights Reports by providing additional detailed information with respect to matters involving international religious freedom.
- National Congregations Study
This study, conducted in 1998 and 2006, collected data about congregations from 1236 congregations. Information was gathered about multiple aspects of congregations' social composition, structure, activities, and programming.
- North America Jewish Data Bank
"The North American Jewish Data Bank is the central repository of social scientific studies of North American Jewry. The Data Banks primary functions are to (1) acquire, archive, and disseminate quantitative data sets and reports, both contemporary and historical, and (2) encourage utilization of the archive through training and provide information about methods for studying Jewish communities."
- Pew Forum on Religion and Public Life
This group seeks to understand the interaction of religion and public affairs. They have a number of surveys and publications analyzing these interactions.
- Social Explorer CU
Explore congregational membership in every county, state and the United States. These data are based on the Religious Congregations and Membership Study, and delivered in partnership with The ARDA organization. Congregational membership data are collected by representatives of the Association of Statisticians of American Religious Bodies (ASARB).
- Statistical Abstract of the United States
This publication produced yearly by the United States Bureau of Census provides selected statistics on religion in the United States.
- Pluralism Project
This project, based at Harvard University, seeks "to help Americans engage with the realities of religious diversity through research, outreach, and the active dissemination of resources." They have a nice collection of statistics and resources on various religious traditions.
- U.S. Congregational Life Survey: A National and International Study of Congregations
This survey was designed to help churches create profiles of their congregations, also presents an overall picture of church attendees and participation. The site reports key overall results, not results of specific churches or denominations.
- World Christian Database
This database provides comprehensive statistical information on world religions, Christian denominations, and people groups. Data are available on 9,000 Christian denominations, 13,000 ethnolinguistic peoples, as well as data on 5,000 cities, 3,000 provinces and 238 countries.