HARI SREENIVASAN:

It may be the world's oldest profession, but little is known about the true economics of the illicit sex industry. It has never really been quantified, until now.

A study done by The Urban Institute, and released today, estimates that the underground sex market in each of seven U.S. cities generates between $40 million to almost $300 million a year. It also found that sex traffickers often operate with formal business models, some even doing market research.

Meredith Dank is the lead author of the report and a senior research associate at The Urban Institute.

So, what was the point of the report? Why did we need to do it in the first place?