rhino, whenthered has already pointed you to threads where the research was discussed at length. Since you clearly can't be bothered to read it, you can at the very least read this:
www.lse.ac.uk/geographyAndEnvironment/whosWho/profiles/neumayer/pdf/Article-for-World-Development-prostitution-anonymous-REVISED.pdf
It that's too much to ask, the summary is:
This paper investigates the impact of legalized prostitution on human trafficking inflows. According to economic theory, there are two opposing effects of unknown magnitude. The scale effect of legalized prostitution leads to an expansion of the prostitution market, increasing human trafficking, while the substitution effect reduces demand for trafficked women as legal prostitutes are favored over trafficked ones. 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.
Please also note from p.75:
This means that the number of prostitutes in Germany is more than 60 times that of Sweden, while having a population (82 million inhabitants) less than 10 times larger. In terms of human trafficking victims, the ILO estimated the stock of victims in Germany in 2004 to be approximately 32,800—about 62 times more than in Sweden (Danailova-Trainor & Belser, 2006).