There has been research about the effect of the closing down windows at 1012 and all the effects for the prostitution in the city. It’s called “Kwetsbaar Beroep” – Fragile Job-

The result of the examination is:
The policy as started is negative for the whole prostitution branch but the elderman will continue the project 1012 and close down windows. The Mayor, Van der Laan, called the report ‘convincing’ but says the negative effect for shutting down prostitutionwindows at the workers is “weakly solid”.

There is no body of evidence that all the prostitutes are  ‘white slaves’ (forced workers) but at some points it ‘burns’.
But as said; no proof. If it’s proofed the window will be closed and the license will be rejected.
It’s hard for the goverment to get into the ‘forced workers circuit’. The chain is too long.
In the report is written: “Probably a cell in Bulgary or Romania stimulates (forces?) a women to work in the prostitution, another cell will do the transportation to Holland and another cell in Holland will do the paperwork, housing and renting the window for the girls.”  It’s hard to get in this world for the police.

Read more at the report!

In the report are a lot of figures about prostitution. The whole report can be downloaded here (pdf-alert!) but only in Dutch!