Article here. Excerpt:

'In 2000, it was reported that the FBI's DNA testing over a three year period had exonerated more than 30% of their 4,000-plus sexual assault suspects. Going further back, in the FBI's Behavioural Science Unit's 1983 study of False Allegations, a total of 220 out of 556 rape investigations - 40% - turned out to be false. Over a quarter turned out to be actual hoaxes (remember the infamous Tawana Brawley, who at 15 falsely accused a number of white men of a marathon three-day gang rape, some of them police officers? At least she got successfully sued for defamation, but that was small potatoes for the havoc she wreaked in those men's lives). About 4,000 allegations of rape a year are levelled in Manhattan. About half never happened. Police officials in New Zealand state that 64% of rape reports are false.'