Global prostitution may be a bigger industry than you think.
There are 40 to 42 million prostitutes in the world, according to a report from Fondation Scelles (via Le Figaro). Three quarters of them are between the ages of 13 and 25, and 80% of them are female.
An estimated 1 million prostitutes live in the U.S., even though it's legal only in Nevada.
In the U.S. and elsewhere most prostitution is unregulated and many workers are forced into prostitution.
The report isn't available online, but here's a map published by the foundation in 2010, which shows the estimated number of prostitutes in various countries as well as number per 1,000 people (data was not available then for countries in green).