Prior to the 2009 Sex Purchase Act, Norway had one of Europe's smallest and least organized markets for prostitution. Women came voluntarily, rented apartments and sold sex from there - without the interference from any pimp.
The introduction of the law has made this process more complicated, according to a report in the Stavanger Aftenblad daily.
"The women are very vulnerable towards the police and to a greater extent on the network and support that pimps can offer," said Guri Tyldum, a researcher at trades union backed Fafo to Aftenbladet.
Tyldum furthermore believes that the criminalization of prostitution has made it more attractive to traffickers.
"The criminalization intended to demonstrate that prostitution is not wanted in Norway. The risk is that the most dangerous and serious form of prostitution that remains," she said.
The Albertine Center in Stavanger has reported a steady increase in the number of prostitutes. The Pro Center in Oslo meanwhile reported significant variations.
The number of active prostitutes at times outnumbers the peak year of 2008, but sometimes there are fewer depending on how active the police are in attempting to tackle the problem. The number of active prostitutes tends to decline following a police operation.
Norway's Ministry of Justice has announced an evaluation of the sex purchase act.