Can't prove it, but I have heard from several people that out of the "big three," - interview, cog, and knowledge test - the cog takes down more people than the other two combined. Most people are reasonably prepared for the interview and wind up over-studying for the ATP test. But countless people are so clueless as to the need to study and research the cog that it is kind of embarrassing. If the gouge you are using doesn't have a full section devoted to the cog test, you have the wrong gouge, or even worst, you have ****ty gouge.