There are more bisexual women than bisexual men. In fact, Dr. Gerulf Rieger, the author of one study, concluded that all women are either gay or bisexual in their sexual turn-ons.
I wouldn’t go that far, but it speaks to the general sexual fluidity of women compared to men. Read on for some surprising studies …
A Pew Research study found that:
In our 2013 LGBT survey, which included a nationally representative sample of 1,197 self-identified LGBT adults, 479 (or 40%) of the respondents were bisexual. And among the bisexuals who were surveyed, a large majority (73%) were women; only 27% were men.
Also, a 2011 study from Boise State University found that “60 percent of heterosexual women admitted to being attracted to other women, while 45 percent had kissed another woman. Fifty percent of those participants also reported same-sex sexual fantasies.”
The most respected sex survey is calledand comes from the . That study tells us that: “Ninety-four percent of men, compared with 83 percent of women, say they’re attracted only to the opposite sex. ( .)”
It is true that there is much more acceptance of bisexual women. Pew Research found that one-third of LGBT adults believe that society has a lot of acceptance of bisexual women — while only 8% believe the same is true for bisexual men. Because of this we might surmise that men might be under reporting their interest in other men.
But when we study physiological arousal, we find that: while men tend to be accurate about what gender arouses them — women greatly under report their sexual interest in other women.  
The men, on average, responded genitally in what Chivers terms “category specific” ways. Males who identified themselves as straight swelled while gazing at heterosexual or lesbian sex and while watching the masturbating and exercising women. They were mostly unmoved when the screen displayed only men. Gay males were aroused in the opposite categorical pattern. … And for the male participants, the subjective ratings on the keypad matched the readings of the plethysmograph. The men’s minds and genitals were in agreement.
All was different with the women. No matter what their self-proclaimed sexual orientation, they showed, on the whole, strong and swift genital arousal when the screen offered men with men, women with women and women with men. They responded objectively much more to the exercising woman than to the strolling man …
Similar results were found in another study where the authors measured eye dilation to gauge arousal. The data was so strong that Dr. Gerulf Rieger, from the Department of Psychology at the University of Essex concluded:
“Even though the majority of women identify as straight, our research clearly demonstrates that when it comes to what turns them on, they are either bisexual or gay, but never straight.”
Here’s the Huffington Post talking about how all the studies point in the same direction:
As far as researchers are concerned, women are. Previous studies have found that there are among women, and their sexual identities are often binary than those of men. This is taken to mean — rightly or wrongly — that women on the whole are more likely to be attracted (at least to some degree) to both sexes, whether they identify as gay, straight, bisexual or pansexual. While this concept is fairly established, researchers have yet to pin down why women throughout their lives.