"...Only about 2% of all rape and related sex charges are determined to be false, the same percentage as for other felonies (FBI). So while they do happen, and they are very problematic when they do, people claim that allegations are false far more frequently than they are and far more frequently than for other crimes. Put another way, we are much more likely to disbelieve a woman if she says she was raped than if she says she was robbed, but for no good reason...."
http://web.stanford.edu/group/maan/cgi-bin/?page_id=297
http://web.stanford.edu/group/maan/cgi-bin/?page_id=297