I wouldn't agree that 8.4% of the prison population is "tiny".
"Statistics from the U.S. Department of Justice show that, as of 2013, there were 133,000 state and federal prisoners housed in privately owned prisons in the U.S., constituting 8.4% of the overall U.S. prison population. Broken down to prison type, 19.1% of the federal prison population in the United States is housed in private prisons and 6.8% of the U.S. state prison population is housed in private prisons. While 2013 represented a slight decline in private prison population over 2012, the overall trend over the preceding decade had been a slow increase." [0]
8.4% of the American prison population is comparable to the total prison population for a european country. finnish are 53 folks per 100k, americans are 655 per 100k...
US's prison system is a human rights catastrophe. China rightly gets lots of criticism for their prison system, and they only have 121 per 100k [0]. Really puts things in perspective. Or look at the total numbers: In china, 1.7 million people are in prison. In the US it is 2.1 million [1]. Yet China has 4.3 times the population of the US...