It is also a case in jurisdictions where it is all legal, because to meet demand it becomes then more profitable to bring (illegally) trafficked women to meet it. In particular, netherlands appear to be one of the highest in trafficking inflows [0, Appendix B].
From [0]:
> Our empirical analysis for a cross-section of up to 150 countries shows that the scale effect dominates the substitution effect. On average, countries where prostitution is legal experience larger reported human trafficking inflows.
[0] https://www.sciencedirect.com/science/article/pii/S0305750X1...