Farming in California is built on trafficked, essentially slave, labor, but I guess the much smaller problems in prostitution are a more romantic target.
Frequency of piecework? I bet there are a lot more instances of "picking a fruit" per year by trafficked farm worker than there are instances of sex by a trafficked sex worker.
Why are you referring to rape as "sex"? Rape is a violent crime every time it happens. I think we can recognize one issue as valuable without putting down the other.
Rape is non-consensual sexual activity. If you want to establish a convention where "sex" only means consensual sex and "rape" only means non-consensual sexual activity, then I'll consent to that. There are far more intellectually honest ways of establishing such a convention than this sort of sideways putting words into someone's mouth.