Came across a textbook called "Practical Aspects of Rape Investigation" that has a chapter on false rape allegations.

The chapter refers to a study done using the records from a police department of an unnamed, average Midwestern city of about 70,000 people. Going back 9 years from 1987, the records showed that 45 out of the 110 total completed rape investigations over that time were completely false, meaning the complainant recanted her claim and confessed that she had made everything up and that no rape had taken place.

There's also an addenda that adds a study from the records of the police departments of two large Midwestern state universities. Going back three years from 1988, the study found that 50% of all forcible rape complaints at the two universities were false.

The authors conclude that "false rape accusations are not uncommon" and that they are "impulsive and desperate gestures of women simply attempting to alleviate understandable conditions of personal and social distress" caused by "the complications and conflicts of heterosexual involvements".

Here's the original website.

The google link wasn't working for me at work, so I had to read the google webcache snapshot.