^ I agree with the kids - maybe not all kids could see them, or they don't acknowledge them as demons. My parents tell me I used to speak to a ghost of a little boy by the side of our house. And I know for a fact my imaginary friends were never human and they followed me to other places.
But yeah, now that tardar points that out, 10% seems more likely. I'd say people who live in places more superstitious would increase the rate of sightings as well; more modernized places that shun those believes would cause it to drop there.