http://news.yahoo.com/s/ap/20060217/ap_on_re_eu/netherlands_prostitution
The story is about many places having an free open house to show that the sex shows are not so bad.
The story also mentions than 7% of the ladies have HIV. That's high. I wonder how they got it. Drugs? Customers (bb?)? Non-customers?
In the early '90's I lived as an expat in Amsterdam on the PC Hofstraat near the red light district. Prior to that the district window shopping was mostly white north Europeans as providers and clients. Very clean and fun. Even toured it with my wife. By the '90's the providers were mostly non-Europeans, and the clients were Arabs. The Europeans established more private clubs. The drugs in Dam Square were rampant, and muggings just two blocks away. The sex shows had deteriorated, the beer was expensive, cover charges to the shows increased, and it ceased to be fun. I asked a Dutch friend how the guys could get it up every half hour and he explained to me the magic of cocaine. So, while not definitive, apocraphlly I would say clientelle, providers, and drugs would be a good bet.
So for the "fun" to return, you are advocating "mostly white north Europeans as providers and clients. Very clean and fun." The so-called ruin of the district has more to do with people and their sexual behaviors and not there ethnicity. As is the same for rise of certain diseases and maladies associated with the sex trade. Since your preference is white and blonde, I'd question whether you really understand people of other cultures... unless, you need your data to be apocryphal...