"Women are so sensitive about being labeled 'sluts' or 'whores' that they are very reluctant to be honest about their sexual behavior, even in supposedly anonymous surveys," said Terri Fisher, who led the study at Ohio State University. "You would assume that when a heterosexual man has sex, a woman is having sex at the same time, but the statistics always suggest otherwise. That can't be true. We thought males would be over-inflating their experience while females under-report it, but that's not what we found." 
  
the proof here