I think the percentages are nonsense and subjective. First off I don't believe there is such a thing as 100% straight (or gay for that matter). This is one of those issues that every time I would bring up would get howls of protests and "Not me, dude! I never thought about another guy!" even in forums that are supposed to be sex positive. But facts are facts in that every human being is capable of being bi-situational and at least a little curious.
In my case, while I have never touched or sucked another dick, I have had experience of masturbating in front of a friend (and vise versa), but since it was during adolescence, I obviously can not go into further details. The closest in my adult years would be the one mini-orgy my wife and I were in where another guy sucked me off a bit while his wife was on my face. While I didn't realize it at first, it really didn't freak me out like it might with the guys who are in denial and I just rolled with it, but it never went further than that. My wife has expressed to me one of the things she wished she got a chance to see when we were swinging is me with another guy and I would not be opposed to it in the future, but since we are pretty much retired from the lifestyle, it's doubtful it will ever happen. Given that she has allowed me many opportunities to watch her satisfy her curiosity with other women, I figure it's the least I can do for her.
Since we are listed as a couple, I'm kind of glad I don't have to list any percentages since I honestly wouldn't be able to answer that. While I can be honest and acknowledge a description of 100% straight would not fit, but then what would the ratio be? Like everything else in life, sexual thoughts and what we find arousing can change from day to day, so I really don't think anyone can answer such a question definitively.