/s/hundreds/thousands working under the kalafa , the euphemism for slavery in middle east. Slavery exists everywhere(yes even in Europe and US) but it's generally not something organized at the state level, it is usually illegal.
http://en.wikipedia.org/wiki/Human_trafficking_in_the_United...
It creates an incentive for the prison industry to lobby for more prisons, tougher anti-crime laws, tougher border crossing penalties, longer sentences. The profits incentivize a total lack of addressing recidivism.
1 out of 4 prisoners in the world occupy a US prison (we account for what? 4-5% of the world's population?). Violent crimes have been trending down over 20 years, but prisoner population as a percentage is at an all time high due to tougher drug convictions.
Also, then there's huge factory farms, which are known to use migrants of questionable citizenship as laborers, and report them to the police when they complain.
The points you bring up about prisoners is interesting. I've always found the moral idea of a for-profit prison as reprehensible.
Every few years since, IIRC, at least the mid- to late-1980s there seems to be a new exposé about various forms of slavery in the Commonwealth of the Northern Mariana Islands (particularly Saipan), though that may have been at least somewhat mitigated in the last few years by Congress' federalization of CNMI labor and immigration policy in 2008.
http://www.newyorker.com/magazine/2003/04/21/nobodies
Since then, they've helped the government rescue over 1,000 people from slavery in the southeast U.S.
http://en.wikipedia.org/wiki/Penal_labor_in_the_United_State...
More detailed account of prison labor in Nevada regarding casinos and construction. http://vltp.net/casinos-prison-labor-strange-bedfellows/
The slave market: http://www.unicor.gov/
You can even get slave labor to operate your call center: http://www.unicor.gov/services/contact_helpdesk/
http://www.nytimes.com/2007/12/03/world/americas/03iht-slave...
The term mostly used nowadays to describe the selling of people is "human-trafficking" even though human trafficking is a little bit broader category. Its common for organized crime to deal in human trafficking.