The Vista Analysis evaluation of Norway's law is available here http://www.regjeringen.no/pages/38780386/Evaluering_sexkjoepsloven_2014.pdf
I find this section in the report very interesting:
The working conditions of men and women in prostitution
The law that criminalises buying sex strengthens the rights of the seller in the sense
that the buyer can be reported to the police. This has given the seller a tool for
managing “bad” customers as well as leading to more careful customers and possible
prevention of violence.
Still, women in the street market report to have a weaker bargaining position and
more safety concerns now than before the law was introduced. At the indoors market,
prostitutes express concerns for “out-door calls”. They prefer to have customers
visiting them at their own apartment or own hotel room. The threshold for reporting a
violent customer to the police also seems to be higher after the law. People in
prostitution are afraid that such actions will come back to halt them at later stages.
Even so, this analysis finds no clear evidence of more violence against women in the
street market after the introduction of the law. It is the customer that engages in
illegal action and thus has the most to fear if reported to the police by a prostitute. The
police have no indications on more violence following the ban on purchasing sexual
services.