Ann Jordan's Issue Paper from Rightswork.org examines the impact of the Swedish Penal Code from 1999. She concludes:
'Not surprisingly, the experiment has failed. In the thirteen years since the law was enacted, the Swedish government has been unable to prove that the law has reduced the number of sex buyers or sellers or stopped trafficking. All it has to show for its efforts are a (contested) public support for the law and more danger for street-based sex workers. Despite this failure, the government has chosen to ignore the evidence and proclaim the law to be a success; it also continues to advocate that other countries should adopt a similar law.'
You can download this 17 page Issue Paper (PDF) below (In English).