Ah. The problem springs from the fact that whenever someone here (in the US) attempts a concerted effort to work out what the rape stats are, whether they're talking about false allegations or just collecting numbers for purposes of tracking violent crime, it's almost always a national agency (usually the FBI) who relies for its numbers on state reporting.

It's hard to decide what criteria to use on a national basis when something that was reported as a rape in Kansas wouldn't have been illegal in California.

As noted in the Wiki link, some states don't think (legally) that men can be raped at all . . . so do you even count the reported rapes of men that occur in states where it's not legally possible to rape a man? If a charge of "sexual assault" is proven to be false in a place where that same charge would have been "rape" in another place, does one count that as a false allegation of rape merely because it happened in Michigan instead of in Alabama?