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The average underground sex act in D.C. costs between $20 and $150.

That’s according to an Urban Institute report released today on how much money commercial sex generates in American cities. The report found that the little-talked about underground sex industry in D.C. was still worth about $103 million in 2007—-that’s the same value of the city’s drug industry, according to the Urban Institute. That represents a 34 percent decrease from the $155 million the industry was worth in 2003.

The study examined the underground industry in seven cities, including D.C., and found that while the sex economy decreased in most cities between 2003 and 2007, it actually increased dramatically in Seattle, growing from $50.3 million to $112 million. Atlanta had the largest underground sex industry in 2007, which was valued at $290 million. That’s up from $238 million in 2003.

Researchers interviewed pimps, sex workers, police, and prosecutors, and used data sets to conduct the study.

In D.C., the underground commercial sex economy includes online and street prostitution, erotic Asian massage parlors, and Latino brothels, according to the study.

There’s no question who’s making most of the money involved: Pimps in D.C. say they averaged about $11,588 in cash income per week between 2005 and 2011. These pimps typically require their prostitutes to meet a quota, which D.C. police estimate to be about $500 a day or $1,000 a weekend. If they meet their quotas, that can bring in up to $234,000 a year per prostitute.

“Because of the city’s location between Maryland and Virginia, much of the underground commercial sex activity occurs without regard to jurisdiction. Furthermore, because of its location along major highways (I-95, I-66, I-270) and its proximity to Baltimore, DC is a significant part of East Coast sex trafficking circuits,” the study reads.

Although the value of the industry seems to have dropped in recent years, cops told researchers that as the parts of the city have been revitalized, the level of adult and child sex trafficking has actually increased.

“Law enforcement reported that the recent economic revitalization of certain parts of D.C. have increased the number of people in the city, thereby increasing the level of adult and child sex trafficking,” the report reads.

Read the summary of the study here and the full study here.

Photo by Graham Blackall via Flickr/CC BY-SA 2.0