While the DailyMail is a trash-site, there is some truth to some of their articles, so the title is kind of right - loosely - but more accurately with data from another OLDER article from better sources. But in that one, it included both sexes.
There is the Kinsey scale, used to gauge homosexuality. I've included a toon-type drawing to show an example below. That scale is the person's sexuality. Point is, almost all people have some experience of same-sex in their lives. Doesn't mean they are gay or even bi. Could be experimental, etc.
Think of the guys here who have very sexual wives that do swapping/sharing/poly and of them, how many of them will have sex with women? A woman I've played with a few times recently, loves cock. She's very straight. yet, we're drunk at a party and she's sucking on my wife's boobies. There are many women I've dated or friends with who are bi-curious or kissed women or played with boobs. Or even talked about it wanting to do so.
There is a cute woman I'd like to have sex with, She'd be a 4.8 on the Kinsey Scale... doubt it'll happen.
The "old days" were simpler, gay or straight. Then you add "bi-sexual" - but that doesn't mean a person is 50/50. Then there is pansexual, and it becomes even much more complicated than that. Then throw in "sexuality fluidity" - which is still, to me - a variant of the Kinsey scale. Fluid means a lesbian is a lesbian, always thinks of women - but at one point, did happen to find herself attracted to a man. (this goes both ways) What makes it different from a bisexual is that a bisexual KNOWS she is bi and is sexually active/interested with both sexes.
Population-wise, about 10% is gay/very bi. But with more data, I'd say about another 20~30% are bisexual. I base this on the number of women I meet that are bi/bi-curious and scientific data. I'm not counting those who tried same-sex once or twice in their life. The M / F ratio is pretty even, just that what is acceptable or repressed will effect who is open or closeted.
More People are not becoming gay, its just more acceptable to be publicly okay.
Sorry guys, but I do enjoy watching my wife eat out another hot chick or the other way around.