Adherents.com includes 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.
Basically, researchers can use Adherents.com to answer such questions as "How many Lutherans live in Wisconsin?", "What are the major religions of India?", or "What percentage of the world is Muslim?" The site presents data 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.