I've seen sources where homosexuals are in the 20% range (which is WAY more believable, because the nation is definitely not 2% homosexual. That estimate isn't correct) and where bisexuals are in the 45% range. Of course, this is flawed in a number of ways, mostly because people have a tendency to lie to themselves, and because the samples taken could simply be a weird group.
Also, there's apparently considerable evidence suggesting that bisexuality doesn't actually exist, but that may be a different debate.
I don't believe that homosexuality is it at 20%. They may be becoming more popular, but saying it is that high is rediculous. (Also, please mind you that lying works in both way. people may lie to themselves that they aren't homosexual, but people may also lie to themselves that they are.) I have not seen evidence that bisexuality does not exists, can you cite me for this?
I gave information earlier, but from all my research, I still conclude that 2-3 percent of the Human race is homosexual and 2 percent is bi-sexual. As for America, I don't think we can put a definate number on it because of immigration and such. Homosexuals do tend to immigrate here to escape persecution, so our number may not reflect the general population of the world.