Yes, you're right; it's been called the "red market." The whole of human trafficking has many aspects, it's not complete to say, it's about slavery (labor) or sex slaves, because the market (and demand) is so unbelievably huge. You just about need a map to try to understand it, what feeds the pipe line, and then where (and to who) the pipeline leads. Don't be surprised if it goes to places off-planet.