Each year since two thousand one, the American State Department has published a Trafficking in Persons Report. It measures efforts by countries to fight human trafficking. This year's report, out Monday, adds the United States for the first time.
The Federal Bureau of Investigation says people are being trafficked into major cities nationwide. Tim Whittman at the F.B.I. is an expert on the problem. He says about twenty percent of the cases involve victims from Mexico -- the largest number of any foreign country.
Bradley Myles is with the Polaris Project, an organization that fights trafficking. He calls it "a very serious problem in the United States." He says some of the victims are forced to work in homes of the wealthy and at restaurants. Activists say some cases of modern slavery involve forced labor in agriculture.
But more than eighty percent of suspected incidents involve the sex trade. That was the finding of a study by the Human Smuggling and Trafficking Center, established by Congress.
The Polaris Project operates a telephone hotline that receives calls from around the country -- from states such as Texas, California, New York and Florida. Bradley Myles says one of the top five cities where calls come from is Washington. Victims in the nation's capital include women from South Korea, China and Latin America. Some victims are American citizens.
Tim Whittman from the F.B.I. says illegal sex businesses often limit their customers to avoid being caught.
TIM WHITTMAN: "If a person, for example, from Korea is brought in to the United States under false pretenses and then forced into prostitution, very much that place where the prostitution occurs is within, then, the Korean community in the United States."
Deborah Sigmund started a group called Innocents at Risk. She says most of the victims of human trafficking come from economically troubled countries.
DEBORAH SIGMUND: "They want to think that they can come to America and have a great job, so it's very easy to fool them."
Tim Whittman says the smugglers often threaten their victims and make it difficult for them to pay their debts. The threat may be against their family back in their home country. But there are other ways to pressure victims to stay.
TIM WHITTMAN: "A common threat is 'If you leave, I'm going to report you to immigration and you'll be arrested. You'll be kept in prison for a long time.'"
But in reality, there is help. Victims of human trafficking can sometimes get a special visa. It permits them to stay in the United States for up to four years. During that time, they can request to stay permanently. But with threats, a language barrier and fear of the legal system, victims are often unwilling or unable to seek help.