By 2010 research-based estimates deemed "very conservative," more than 200 Minnesota girls are sold on the Internet for sex every day. Their average age is 13.

On average, two-thirds of them will stay in the sex trade until adulthood. During that time, they'll typically endure a wide range of trauma -- dehumanization, assaults, sexually transmitted diseases, unwanted pregnancy and sometimes much worse.

An obvious moral case exists for societal intervention to put a stop to this outrage. Advocates for doing so say they now have the ammunition to make an economic case, too.

A new economic cost-benefit analysis of government-funded early intervention in the lives of runaway and homeless girls has been conducted by researchers from the University of Minnesota and Indiana State University at the behest of the Minnesota Indian Women's Resource Center. It concludes emphatically that the prevention of early adolescent sex trafficking is in taxpayers' best interest.

The 30-year return on state spending on housing plus services for the projected 496 Minnesota girls per year who would benefit from them is an eye-popping $34 for every $1 spent. That's $58,229 in 30-year savings per girl served.

Researchers came to that figure with a thorough assessment of sex trafficking's cost for society. For a crime some ill-informed people consider "victimless," the impact is surprisingly large. Researchers identified 16 adverse effects that are both widespread among sex-trafficked girls and taxing for the public purse. They include repeated physical injuries, sexually transmitted diseases, unintended pregnancies and recurring criminal-justice expenses.

To state lawmakers' credit, Minnesota law was changed in 2011 to treat sex-trafficked girls under age 16 as victims of a crime, not as criminals themselves. No more will brutalized girls as young as 11 or 12 suffer the additional trauma of juvenile detention.

But where such a girl will go after an arrest or her voluntary surrender to authorities is a matter for Gov. Mark Dayton and the 2013 Legislature to address. Sex-trafficking victims typically aren't able to go home again. Conventional homeless shelters and foster homes aren't appropriate settings for them, either. They need more specialized settings that offer treatment for their physical ills and therapy for their mental and emotional ones. They also need to be set on a pathway to a healthy, self-sufficient life.

Today only four homeless shelter beds in the Twin Cities are suited for this mission. Advocates say at least 50 per night are needed. A group of more than 80 Minnesota stakeholders, orchestrated by the "Minnesota Girls are Not for Sale" campaign of the Women's Foundation of Minnesota, has been at work this year devising a proposal to do better.

Foundation president Lee Roper-Batker said the group expects to ask the 2013 Legislature to establish a housing-plus-services program that will cost state taxpayers between $10 million and $15 million per biennium, plus some initial costs for facilities.

Roper-Batker said the group will also bring to the Capitol a sense of both urgency and opportunity. The urgency comes from indications that the number of Minnesota girls trapped in sex-trafficking arrangements has been rising since the onset of the Great Recession.

The opportunity comes from heightened awareness of the problem around the country, and the knowledge that other states are watching how Minnesota responds to the Women's Foundation campaign. Even the possessor of the nation's biggest bully pulpit is involved (see box, above). "Minnesota is rich with expertise and leadership on this issue," Roper-Batker said. "There's heightened interest among the public, too. The time is now. Enough is enough."

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