Websites are highly contradictory, about how highly the World Health Organization ranks OCD among disabling illnesses. “Fourth,” “tenth,” “twentieth” are some of the figures cited. Part of the reason for the discrepancy is that the WHO have revised their own ranking downwards, but even at twentieth, it is still remarkably high.
Worldwide research consistently indicates that one to three percent (some say two to three percent) of people have OCD. In the U.S. alone, millions of people have OCD. By comparison, some U.S. surveys suggest this equals the number of Americans who claim to be atheists, or roughly the number of full-time farmers.