According to the National Institute of Justice (see the link below), it is estimated that 4.5% of prison inmates, or 60,5000 people, have reported sexual violence, assaults, or rape in prison (the data comes from the Bureau of Justice Statistics). The Prison Rape Elimination Act (PREA) of 2003, passed by the U.S. Congress, required the U.S. Department of Justice to make elimination of rape a priority in prisons. According to research by Zweig and colleagues (see the reference below), many states are implementing sexual violence policies that involve the prevention, detection, and response to sexual violence in prisons. Several states have made a commitment to changing a prison culture in which violence is condoned, and many states require prison staff to undergo training related to sexual violence. Staff are critical in reducing sexual violence and responding to it in appropriate ways. Therefore, staff in prisons have been training on the procedures for reporting incidents and on the way to provide services to victims, though several barriers remain, including the unwillingness of some victims to report sexual violence and the delay in reporting violence.
Zweig, J.M., R.L. Naser, J. Blackmore, and M. Schaffer, Addressing Sexual Violence in Prisons: A National Snapshot of Approaches and Highlights of Innovative Strategies, Final Report (pdf, 187 pages) , final report submitted to the National Institute of Justice, January 2007 (NCJ 216856).