This link is to a study published in 2016 by the New York based Center for Court Innovation. It is a long report running to 165 pages. In total, interviews were completed with 949 young people ages 13-24 across the six sites. Ranging from 30 minutes to two hours, the interviews included both closed-ended and open-ended questions on a wide range of topics.
Among its many findings is the disconnect between the public understanding of sex trafficking and the Federal definition that claims all underage sex workers are sex trafficking victim with or without a person who exploits an individual in the sex market through coercion, control, or force. So this study shows 15% working with a pimp, but 80% meeting the Federal definition of sex trafficking victim.
Youth Involvement in the Sex Trade: A National Study | Center for Court Innovation