The British male sexual-violence support organisation Survivors UK recently carried out a study on behalf of the Greater London Authority to find out reporting rates among men.
Of the 500 male rape victims included in the survey, 3.9% reported their rape to the Plod.
Perhaps the other 96.1% are lying about having been attacked. Personally, I don't think so.
Reporting rates among women are believed to be higher. But not hugely so, even today. A very large study by the U.S. Department of Justice in 2010 found that two out of three rapes of women are never reported.