The rate of accusations police are confident are false, many of which don't make it to trial, is low. The rate of accusations proven, beyond reasonable doubt in the minds of the jury, is similarly low.

The actual figures are an unknown proportion of the vast majority of the middle (further complicated by the large, and variable, proportion of sexual assaults that go unreported) and any study requires a lot of guesswork. The decision to report an assault, accurately or otherwise, is also evidently not an event independent of other reports of similar assaults, especially since many come after the allegations and name of the accused are revealed.