A new Justice Department study shows that allegations of sex abuse in the nation’s prisons and jails are increasing — with correctional officers responsible for half of it  — but prosecution is still extremely rare.

The report, released today by the Bureau of Justice Statistics, takes data collected by correctional administrators representing all of the nation’s federal and state prisons as well as many county jails. It shows that administrators logged more than 8,000 reports of abuse to their overseers each year between 2009 and 2011, up 11 percent from the department’s previous report, which covered 2007 and 2008.