There are a lot of statistics about prostitution and sex trafficking, and there is a lot of misinformation and junk science out there – not to mention the dozens of websites that compile and deconstruct that data. This website is about Alaska, but here are some links to relevant national statistics.
Operation Cross Country is an ongoing, intermittent FBI project where every once in a while they sweep the country “rescuing” (ie, arresting) youth in the sex trades and also arresting adult prostitutes and pimps. In 2009 they visited Alaska twice and found no children to rescue. Here is a round up of rescues, pimps, and other arrests by city and operation.
Prostitution Arrests by year – Norma Jean Almodovar is a sex worker rights activist who got her start working as an officer for the LAPD. She’s compiled arrests of minors and adults by year according to the FBI. I highly recommend reading all of her research.
Sex At The Margins: Migration, Labour Markets, and the Rescue Industry is a great in depth look at sex trafficking on a national and international scale.