You might reason that men are experiencing more harassment, which might be the case, but that probably does not explain the rise completely. Officials suspect that male victims have become less reluctant to come forward.
And while some male complainants experience harassment from female colleagues, men-on-men harassment is the most common type reported. This often includes harassment for perceived or actual homosexuality as well as unwelcome same-sex sexual advancements. My guess is that while sexual aggression from female co-workers does exist, some men still want to avoid the stigma associated with reporting this — since you know, real men are supposed to want sex all the time from any woman. Or perhaps we're supposed to find "horny" women comical and nonthreatening. These assumptions don't change the fact that any sexual harassment victim, male or female, can have their well-being and ability to work negatively impacted by a hostile work environment.
Have you heard of any cases of female-to-male sexual harassment?