Unlike sex trafficking, survival sex is not a financial transaction. Survival sex is, quite simply, exchanging one's body for basic subsistence needs, including clothing, food, and shelter. While estimates vary, most figures put the homeless youth population in the U.S. around 1.5 million. These are kids under the age of 18 who were often either kicked out of their homes because of dwindling financial resources or ran away to escape an abusive, volatile environment. Once on the streets, these teens rapidly find that clothing, food, and shelter are far from guaranteed. Without any money or the ability to get a job, many are forced to rely on their bodies as the only commodity they possess.

According to an article published in the New York Times in 2009, nearly one-third of homeless youth end up participating in survival sex during their time on the streets. While survival sex also entails exchanging their bodies for drugs and alcohol, youths are most frequently seeking shelter. After leaving home, they scramble to find abandoned buildings, riverbanks, underpasses, and rooftops to sleep at night. When their situations become desperate enough, runaways can end up having sex with someone in exchange for a place to stay, however brief.

Such behavior rarely occurs in a vacuum. As reported by Covenant House in May 2013, survival sex and sex trafficking, while legally and definitionally distinct, have significant overlaps, with the former often serving as a segue to the latter.

In some cases, teens begin sleeping with older men in exchange for a place to stay, but over time, the man starts forcing the girl to have sex with his friends for cash. In others, young girls find themselves in self-preservation-minded sexual relationships with providers or "sugar daddies," but are abruptly kidnapped or exploited by other predators in the same social circles

Covenant House recounts the horrifying story of a young girl who, by the age of five, had already been repeatedly raped by an older family member. As a teenager living on her own, she engaged in prostitution/survival sex when she was unable to make the rent. At the age of 19, she attended a party thrown by people she had just recently met, and was kidnapped at gunpoint and forced into sexual slavery for three months until she finally escaped.

This appalling turn of events may be unique in the extreme levels of abuse at different phases of the girl's life, but their relationship to one another—that is, the pattern of sexual abuse—is not. The connection between prostitution and a history of childhood sexual abuse is staggering.

Some studies have found that 70 percent of female prostitutes were sexually abused as children; others peg the figure at closer to 85 percent. The bottom line is that prostitution, especially among teenagers, is rarely if ever an act of free will; it's born out of a lifestyle that destitute young people are forced into.