Shaming the men who pay for sex

The US has a federal anti-trafficking law and New York state has its own tough penalties.

Though strong laws are in place, the problem is enforcing them. Convicting pimps is difficult as their victims are often too terrified to give evidence.

Women can be offered special visas, which allow them to work legally if they co-operate in trafficking investigations. Reducing the demand for prostitution is seen as the key to ending sex trafficking.

In Brooklyn, New York, there is an initiative called John School. Men convicted of soliciting prostitutes learn about the dangers to their health - and how the women they're paying for sex with may be trafficking victims.

Produced by the BBC's Laura Trevelyan and David Botti.