Wikipedia
Adherents.com is a website that aims to collect and present information about religious demographics, established in 1998. It is the largest pool of such data freely available on the internet. As of January 2010, the site contains approximately 44,000 references on over 4,300 faith groups. The site offers its information sorted geographically, focusing on the number of adherents of a given denomination in a specific region or country.
According to the site, Adherents.com 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." The website is a private project by Preston Hunter, a computer programmer of Texas, USA. It is neither supported by or affiliated with any organization.
Its compete.com rank as of December 2009 was 12,760, its daily ads revenue estimated at USD 58.