Do you mean "less than 3% of inmates are ever raped in jail"?
Or "less than 3% of inmates admit to being raped in jail"?
Hmm that may be a valid point.
"It was
conservatively estimated by the Department of Justice (DOJ) that approximately 1 in 10 inmates were assaulted in 2012, and as prison populations continue to grow, it can be assumed that this number has only increased in the past two years."
source:
http://lawstreetmedia.com/blogs/crime/rape-part-sentence/3% may not be accurate. If they're "conservatively estimating" 1 in 10 are being "sexually assaulted" in some way, it's probably 15-20% in reality.
But be aware that "sexual assault" includes things like touching and molestation, not necessarily full on rape.