A 2009 research report, 100 Countries and Their Prostitution Policies, lists attitudes worldwide toward commercial sex.

Prostitution is legal in 50 countries and illegal in 39, including China. For the other 11, laws vary depending on place, age and gender.

The research, which was conducted by the nonprofit public charity ProCon.org, showed that Zurich, Switzerland, has about 11 prostitutes per 1,000 people - similar to the rate in Amsterdam, The Netherlands, which is known for its sex trade.