Niklas Jakobsson, PhD, Research Fellow at Norwegian Social Research (NOVA), and Andreas Kotsadam, PhD, Postdoctoral Fellow at the University of Oslo, Norway, stated in their Feb. 2013 study titled "The Law and Economics of International Sex Slavery: Prostitution Laws and Trafficking for Sexual Exploitation," published in the European Journal of Law and Economics:

“Using two recent sources of European cross country data we show that trafficking of persons for commercial sexual exploitation… is least prevalent in countries where prostitution is illegal, most prevalent in countries where prostitution is legalized, and in between in those countries where prostitution is legal but procuring illegal.”

Feb. 2013