Milwaukee has become “the Harvard of pimp school” and Wisconsin is a hub of human trafficking, an expert has said in the wake of an FBI sting last month in which nine adolescents were rescued from commercial sexual exploitation, meaning Milwaukee is tied with Las Vegas for the third highest number of young people rescued during the FBI raids across the US.

Denver topped the list, with 20 young people rescued, and Detroit was next with 19. Over the past four years, however, Milwaukee has consistently ranked among the top five cities in the nation for the recovery of trafficked adolescents, the FBI said. In 2011, it reported the highest number.

But this is just the tip of the iceberg, believes Dana World-Patterson, chair of the Human Trafficking Task Force of Greater Milwaukee. “There’s no way that the numbers are accurate,” she told the Guardian. “Milwaukee has been considered the Harvard of pimp school, Wisconsin, the hub of human trafficking.”

Unpublished data reported to the Guardian by a local trafficking prevention project, Proactive Outreach for the Health of Sexually Exploited Youth, counted 133 minors who had been trafficked or were suspected of having been trafficked or exploited over the course of 2014.

The youngest child to have been trafficked between 2010 and 2012 was 12, according to a 2013 review of Milwaukee police records by the Milwaukee Homicide Review Division, while most of the 77 young people identified as trafficking victims in that period were between 15 and 17. The vast majority were African American.

While available data indicates that the majority of the young people being trafficked are girls from the city’s north side, advocates say that boys are also affected, and that the traffickers include women as well as men.

Engaging a minor in a sexual act for money constitutes trafficking under Wisconsin and federal law because minors are not legally able to give consent.

Milwaukee police officials declined to speak with the Guardian on the matter.

“Some of the biggest risk factors that we’re seeing are kids that are running away,” Dr Angela Rabbit of the Children’s Hospital of Wisconsin told the Guardian. “A very high proportion of them have [suffered] physical abuse or sexual abuse even before their entrance into the sex trade, so they’re already coming into the sex trade with all of these traumas and behavioral characteristics that make them vulnerable to traffickers.”

An adult survivor of trafficking, Nancy Yarbrough, said she fell for the so-called “Romeo effect” when she was 16, beginning a relationship with and eventually leaving home for the man who became her pimp. Yarbrough said prior sexual abuse made her vulnerable to the trafficker’s advances, but so was the lifestyle he claimed to offer her.

“He made me believe that everything he said was true,” she said. “So when they speak about a fairytale that’s given to you, you take it hook, line and sinker because you really want to believe that it’s true.”

Young people often find themselves stigmatized when they speak up about having been manipulated for sex, Claudine O’Leary, a youth advocate who has worked with young people involved with the sex trade for more than two decades, said. Parents can stop speaking to them, among other consequences.

“People start getting much more restrictive,” she said. “So any kind of freedom that you had is gone at that point. And then they start even bringing things up. So let’s say a friend of yours does buy you that or lends you a jacket, and you show up with that jacket, and people are like ‘where did you get that jacket?’ And so for ever more, a week later, a month later, a year later, people are bringing it up and saying like ‘I know you’re doing it again.’”

While young people face obstacles being heard and supported, O’Leary said, Milwaukee’s “embedded” pimp culture throws up other barriers to escaping it. “In the same way that there are cop bars, there are pimp bars, and people know it.”

O’Leary described a thriving underground economy, in which people depend on different aspects of the sex trade directly or indirectly. Providing security, driving people, and doing hair for women who work at clubs were all kinds of informal employment O’Leary listed that can be enmeshed with the sex trade. Likewise, when pimps are brought to court, O’Leary said that their supporters will often fill half of the room, which can intimidate a victim’s family and friends.

Pimps have also been described as visiting a trafficking victim’s place of work to entice them back into the trade or cruising group homes to find young people who are disaffected with the environment and are more vulnerable to appeals to perform sex work. The Milwaukee Journal-Sentinel published a report this week of “pimp roundtables” at which the city’s pimps shared information about the business and their sex workers.

Ultimately, O’Leary said, given the number of people who may search for work for months or years, Milwaukee’s economic disparity “is creating a situation with a lot of vulnerable youth”.

Wisconsin was recently found to have the highest African American unemployment rate in the nation. Fewer than half of the adult African American men in Milwaukee, a majority black city, are formally employed.

Adding further to a dismal economic picture, In These Times reported that the city had lost 80,000 jobs in manufacturing since the 1970s while median wages dropped by nearly 22% in the decade between 1999 and 2010.

Such economic hardship can stymie those who want to get out of the sex trade, according to Dr Wendi Ehrman, an adolescent health practitioner at the Children’s Hospital of Wisconsin. Ehrman cautioned that while raids like the FBI’s in October can help rescue some young people from traffickers, removal may be short-lived if young people are faced with the same situation they left earlier. “If they return home without those services [mental health services, stable housing, access to job and educational opportunities etc] in place, or wherever they are sent back to, it’s very likely that they will go back to what they know, and that’s the problem.”

Milwaukee-based FBI agent Heather Wright agreed. “I would like to see stiffer penalties for the traffickers and more services for the individuals being trafficked. There is a reason that they are being trafficked, and they are being being targeted because of the lack of supervision and resources for the kids, and adults for that matter.”

State Representative LaTonya Johnson of Milwaukee has introduced a “safe harbor” bill that would decriminalize sex work for minors, but she acknowledged that even if the bill were to pass, obtaining the funding needed to put the necessary social and health services in place would be “an uphill battle”.

Another bill would mandate children be accompanied by an advocate during interviews with law enforcement, which O’Leary says has more chance of delivering results.

Even these bills, O’Leary said, fail to address the systemic nature of Milwaukee’s trafficking problem. “We fix this situation – and this is going to be big – by this idea of addressing and changing the deep, deep economic inequality that exists in our system. We address it by actually reducing the incidence of sexual violence.”