I have no deep knowledge of the subject, but it seems that false accusations of sexual assault are not common:
Reliable studies consistently measure the rate of false reports as 2% to 10%. For example, an analysis of ten years of cases reported to a University police department involved setting coding criteria in advance, reviewing case summaries, meeting with police officials to review the cases in more detail, and establishing coding reliability by comparing the classifications made by two research teams across all 136 cases. This study found that only 6% of the cases were false allegations (
Lisak et al., 2010). A
2014 study of sexual assault cases reported to the Los Angeles Police Department used quantitative and qualitative methods to review reports and analyze detective interviews. The study found that 4.5% of cases were false reports. These results are consistent with other well-constructed
international studies.
As with any crime, false reporting of sexual assault does occur; however, it is very rare. When it does occur, it is both incredibly harmful to the falsely accused and extremely damaging to survivors of sexual assault who find themselves subject to stereotypes and disbelief as a result.
False reports of sexual assault are dramatically overestimated. Poorly constructed studies and a lack of understanding of the dynamics of sexual assault contribute to this problem. In rigorous research, rates of false reports are consistently very low, ranging from 2% to 10%. This is similar to...
www.brown.edu
Please forgive the Wikipedia reference, but it's got some more info here:
Crown Prosecution Service report (2011–2012)
A report by the
Crown Prosecution Service (CPS) examined rape allegations in England and Wales over a 17-month period between January 2011 and May 2012. It showed that in 35 cases authorities prosecuted a person for making a false allegation, while they brought 5,651 prosecutions for rape.
Keir Starmer, the head of the CPS, said that the "mere fact that someone did not pursue a complaint or retracted it, is not of itself evidence that it was false" and that it is a "misplaced belief" that false accusations of rape are commonplace.
[29] He added that the report also showed that a significant number of false allegations of rape (and domestic violence) "involved young, often vulnerable people. About half of the cases involved people aged 21 years old and under, and some involved people with mental health difficulties. In some cases, the person alleged to have made the false report had undoubtedly been the victim of some kind of offence, even if not the one that he or she had reported."
[30][31][32]
en.wikipedia.org