Launching a startup? Market to these guys
corp.pipl.com
corp.pipl.com
It's be interesting to research the reasons behind that statistic. It could be that women are more risk averse so they don't sign up as often. Or that women have a higher bar for giving up the privacy of their email address and startups are failing to win their attention. Or startups market to their peers at the beginning, and as most startups are male-led that means they don't get the message to women as often.
There could well be a 'betali.st that appeals to women' opportunity here.