Yeah, I searched this one up and down and sideways a few years ago. WHO does not actually provide rankings in the cited article. I went back to 1980 and found an article that named the options but did not numerically rank in the way everyone cites them. It reminds me of the xkcd cartoon about citation genesis. Everyone now quotes Weissinger quoting WHO, and no one goes to any original source.
1/12/13 at 6:50am