We talk about jobs and taxes and pay checks, but here’s what we don’t talk about: right here, in the United States, there is a thriving underground economy based on selling children for sex. If sex sells, then business is good. It was almost a billion dollars, according to an Urban Institute 2014 study. But these dirty profits come at a huge cost. This is how sex traffickers do business. It’s all about supply and demand. First, they need someone to sell.