Anecdata

Andrew Sullivan has a very annoying habit of giving was too much credit to anecdotes relayed by his readers. His most recent letter from a reader shows how misleading it can be to rely on anecdotes:

Unfortunately, in the mid 90s, I spent just over four years (52 months) in prison. 

[snip]

While there were instances of sex abuse in some of the prisons I visited, they were few and far between.

[snip]

I firmly believe that the sex abuse in prison is not a significant enough problem to warrant any action from the federal government.

You can rely on this compelling anecdote, or you can rely on the US Justice Department's Bureau of Justice Statistics:

According to the report, released today by the Bureau of Justice Statistics (BJS), “Sexual Victimization in State and Federal Prisons Reported by Inmates, 2007,” 4.5 percent of the state and federal prisoners surveyed reported sexual victimization in the past 12 months. Given a national prison population of 1,570,861, the BJS findings suggest that in one year alone more than 70,000 prisoners were sexually abused.

While the sexual abuse rate is not as high as the "they're raping everybody in here" image often portrayed in the media, it is way higher than a decent society should ever allow it to be. Or, if you didn't happen to be abused during your years in jail, "not a significant enough problem to warrant any action".