I found the bit about the US prison population growth rate interesting. The author points to a Reuters article that pegs prison population growth rate at about

I found the bit about the US prison population growth rate interesting. The author points to a Reuters article that pegs prison population growth rate at about 4% (http://www.reuters.com/article/bondsNews/idUSN0727506220071007 http://www.reuters.com/article/bondsNews/idUSN07275062200710...), and, according to Google, the US population growth rate is 0.883%. I wonder why the former is so much higher than the latter, and how those numbers compare to historical trends.