One out of 100 Americans are imprisoned. According to the Sentencing Project (http://www.sentencingproject.org), prison populations have increased 500 percent over the last thirty years in the United States.
The answer to this question is too vast to answer here but I have had some recent insight into this in the oddest of places. Introversion, a British game developer, has developed a game called Prison Architect. The game appears similar to SimCity but the tutorial mission suggests something much more subtle and disturbing. The task assigned to you as a new warden in this prison is to build an execution chamber for a prisoner sentenced to death. That means building a holding cell for the condemned, which must have a bed, a window and a toilet. And the game suggests that if you are feeling charitable you can put a bookcase in there too. You then plan out the execution chamber itself, which means running electrical cables from your power station and plumbing to make sure the water fixtures in the prisoner