You make a good point and this point has indeed been argued. I can't speak for the quality of the research, but one conclusion was that if demand exceeds domestic supply, legalization will increase trafficking in high income countries. Which makes sense from an economic point of view.
I still think the problem is the trafficking and not the prostitution so much, and that all efforts should be put towards combatting trafficking by any means possible.
Even if protitution was legalized, I have no problems convicting johns for enabling or benefiting from human trafficking, if done so knowingly. This isn't much different from age of consent and could be solved in a similar way.
Criminalizing prostitution also further victimizes the victims of human trafficking.
Prostitutes that have been human trafficked risk arrest and/or deportation just for stepping forward and exposing the human traffickers. Guess whose interest that plays into?
I still think the problem is the trafficking and not the prostitution so much, and that all efforts should be put towards combatting trafficking by any means possible.
Even if protitution was legalized, I have no problems convicting johns for enabling or benefiting from human trafficking, if done so knowingly. This isn't much different from age of consent and could be solved in a similar way.