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What is the source of the Pope's power? Well, one obvious reason is that Catholicism still commands a fair number of adherents. According to the CIA World Factbook, close to 17% of the world's population is Catholic. It's the largest denomination in Christendom. Only Muslims have more adherents, but that's deceptive since the CIA combines Shi'a and Sunni Muslims. From an international relations perspective, if power equals numbers, there appears to be a tripolar distribution of religious adherents between Catholics, Hindus, and Sunni Muslims.