The sale of sex has shifted online as pimps use underground websites, social media and mobile apps.
The findings are in a new study by criminologists at Michigan State and Loyola University-Chicago where they interviewed pimps in Chicago and Atlanta.
Lead study author and head of the MSU School of Criminal Justice Mary Finn says the pimps make a lot of money.
Finn says pimps use the underground sites to advertise to avoid being caught by police.