Map: The world's prostitution economy

The world’s oldest profession is also an in­cred­ibly large one, stretching from San Francisco to Osaka, according to a new report.

There are 40 million to 42 million prostitutes in the world, according to the report from Fondation Scelles. Some 80 percent of them are female, and 75 percent are between the ages of 13 and 25.