In this old post I showed that since the early 1990s, young women have grown more and more sexually experimental with other women. There was no similar steady trend among young men: women's sexuality is more fluid than men's, at least when women are under 30 and more risk-taking. So whatever cultural causes are at play here will affect female more than male behavior.
That post covered data through 2010, but there have been two additional waves of the General Social Survey in '12 and '14 that we can check to see what's been going on since.
In short: young women are still more experimental than they were even at the end of the last decade.
Before I used three related variables to measure heterosexuality -- the sex of your sex partners over the past year, over the past five years, and how many men / women you've been with since turning 18. I'll stick with the last one -- how many women has a woman been with since turning 18 -- because that reveals earlier experimentation that may not have continued up through the date of the survey.
I'm also restricting the respondents to white women, to control for changing racial demographics among young people over time. "Young" here means aged 18 to 29 (same picture if you use 18 to 24; the wider range is used to boost sample sizes).
As of 2008 and '10, young women were about 89% heterosexual -- meaning they said 0 female partners during their adult lives. In '12, it fell to 87% and in '14 it fell again to 83%. This is down from a high of 95-100% heterosexuality among young women way back in the early 1990s.
Now, some of those who answered "zero women since I turned 18" have experimented with girls before turning 18, but not after. That adds in another several percentage points to the 17% who have behaved bi-curiously in adulthood. The more relevant variable is how non-heterosexual she has been after reaching sexual maturity. If she messed around with guys in high school but has been celibate from 18 to 25, she's still not a virgin.
So perhaps 20-25% of young women these days have experimented with other women during their sexually mature lives. The only silver lining there is that they're still a numerical minority.
It's true that such experimentation declines during their 20s, and is nearly done with by age 40. So at least early deviance doesn't last into mature deviance. On the other hand, whatever warping effects there are of being sexual with someone of the same sex, will persist well into middle or old age. It only takes those handful of times to yield the effects.
That could be disease-related. Men get oral/throat cancer from going down on women whose reproductive tract is infected with HPV (which gives the women cervical cancer). Bi-curious young women who go down on other women expose themselves to this risk, too -- something that wouldn't have happened if they had only been with men, who don't transmit HPV through fellatio. And it may only take a handful of bi-curious episodes to infect her. Remember that the data above are the number of women she's been with -- they don't say how frequently or infrequently she was sexual with another woman.
Then there are the psychological scars of same-sex experimentation. On the one hand, women are good at rationalizing and suppressing acts of their past that would lead to present cognitive dissonance or anxiety. On the other hand, that time when she repeatedly hooked up with other girls in college... seems difficult to forget. Women also experience sexually related psychological pain more forcefully than do men, especially if it involves feelings of vulnerability, naivete, and being taken advantage of.
And don't kid yourself -- the other woman, who's probably lesbian or girl-leaning bisexual, knows that this bi-curious girl is just going through a phase, is unsure, awkward, etc., but is not about to pass up an opportunity to add another notch on the bedpost. That feeling of being gullible and taken advantage of, in the most physically vulnerable state she can be in, will be rattling around her mind forever. It only takes once.
Male homos get most of the attention, pro and con, because they're the most flagrant flamers out there (other than the outright trannies). But they're still only 2-3% of men, and bi-curious experimenters add on at most another 5%, neither of which has been getting worse over the past several decades. That's nothing compared to the 20-25% of young women who are flouting normal sexual behavior by messing around with other girls during adolescence and young adulthood, a figure that continues to grow worse over time.
They should therefore be the next big target for attacking laissez-faire sexual norms. To the more rebellious ones, shame them about getting a boyfriend / husband, or keeping their horniness to themselves if they're too awkward around boys. To the more confused ones, meet them half-way and show them how unproductive and ultimately damaging it will be to them, physically and psychologically, to pursue the fool's game of short-cuts toward pleasure.
And of course, mercilessly mock the men who enable these trends by reminding them that girl-on-girl leaves them sexually rejected by not one but two girls, and is the fantasy of a defeatist loser. Also, that trying to sexually resonate with either one of the girls makes them a crypto-tranny (or in medicalese, latent transgender).
This fight should prove easier than the fight against Sodomite marriage, since the other side does not brand themselves with concepts like "love" and "marriage" and "equality," but with "slut" as in "slutwalk," "boo slut-shaming," and so on. And their outside enablers are not middle-of-the-road types, but sexually frustrated dorks who whack off to lesbo porn. Their image in the mass media is not a pretty lie such as the eccentric uncle in a family sit-com, but the ugly truth like Demi Lovato slutting it up in a heroin-dazed music video.
GSS variables: numwomen, year, sex, race, age