I found a ProPublica article with broken links to government sources that says around 8% of prisoners were housed in private prisons in 2010. A Pew Research article[0] shows that private prisons have housed between 5-8%, but in 2016 out of 2,162,400 total prisoners[1] only 128,063 of them were in private prisons[2], which is about 6%.

I wholeheartedly agree that 6% of the prison population (128,063 people!) is a situation worthwhile of positive change. But I remain skeptical that it's those damn private prisons that are ruining everything. Mostly I think it's debacles like the drug war that need real immediate attention and change before things will significantly improve.

[0]https://www.pewresearch.org/fact-tank/2017/04/11/u-s-private...

[1]https://www.bjs.gov/content/keystatistics/csv/Total_correcti...

[2]https://www.criminaljusticeprograms.com/articles/private-pri... again citing the BJS.