A U.S. national survey of inmates in 2008-09 found, based on inmate self-reporting, an estimated 21,100 inmate victims of inmate-on-inmate nonconsensual sexual acts. The same survey found an estimated 47,000 inmate victims of staff sexual misconduct.^ About two-thirds of these sexual victimizations are rape or rape/sexual assault in crime victimization categories. These statistics underestimate the number of victims and incidents of victimization over a full calendar year. Better estimates indicate about 900,000 rape/sexual assaults of inmates in the U.S. per year.

Compared to findings from inmate sexual victimization surveys, U.S. correctional authorities report a much smaller number of inmate sexual victimizations. For calendar year 2008, U.S. correctional authorities reported 2,343 inmate allegations of inmate-on-inmate nonconsensual sexual acts and 2,528 allegations of staff sexual misconduct. Across calendar years 2007 and 2008, correctional authorities investigations found 12% of the fully investigated allegations to be substantiated (alleged sexual victimization found to have occurred), 57% unsubstantiated (evidence insufficient to find whether the alleged sexual victimization occurred), and 32% unfounded (alleged sexual victimization found not to have occurred). The corresponding figures for fully investigate allegations of staff-on-inmate sexual misconduct were 19% substantiated, 53% unsubstantiated, and 28% unfounded.^

The orders of magnitude difference between inmate self-reports and correctional authorities’ reports suggests that many incidences of nonconsensual sexual acts and sexual misconduct aren’t reported to correctional authorities. At the same, about 30% of such allegations reported to correctional authorities are found upon correctional authorities’ investigations to be false. Moreover, investigations find sufficient evidence to substantiate only about 15% of those reported allegations. These are allegations of relatively serious sexual victimizations. They don’t include inmate-on-inmate abusive sexual contacts and staff sexual harassment of inmates. Surveying sexual victimization involves difficult conceptual issues. Both under-reporting and false reporting of relatively serious sexual victimization are quantitatively major issues.