10. Scientology
9. Agnosticism
8. Atheism
7. Taoism
6. Satanism
5. Confucianism
4. Hinduism
3. [spoiler]Buddhism[/spoiler]
2. [spoiler]Judaism[/spoiler]
1. [spoiler]Christianity[/spoiler]
Honorable Mentions: Catholicism and Sikhism
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Skipped Islam? No bigy, only 1.6 [b]billion[/b] people.