I have very mixed feelings about this. I believe in self determination and that government should have no say in what you do with your own body. Therefore I think prostitution should be legal. However living in the Netherlands where it has been condoned/legal since a long time, it seems to have not dialed back human trafficking, in some cases maybe even making it worse. I'm similarly conflicted about drugs. In theory, everyone should be able to ingest whatever they feel like, but the opioid crisis in the US is exactly what happens when you can get easy access to hard drugs.
My job involves dealing with organized crime on a policy level and what I'm going to say is probably going to be ignored in this debate as it is everywhere else but here goes:
There are NO reliable figures on the scale of human trafficking ANYWHERE.
It's what we call a 'dark number' in law enforcement - we know it's there and some outward effects of human trafficking are measurable (like, say, how much money we seize when we roll up a gang or how many health workers notice signs of violence with prostitutes) but the real number of people trafficked / enslaved / exploited is completely opaque.
I swear, hand on heart, that anyone who makes sweeping statements about the rise or fall of human trafficking is twisting these handful of measurable quantities to suit their agenda. Yes, even high ranking police officials.
We. Just. Don't. Know.
People who go even further and use these unreliable indicators to find correlation or causation between legality of prostitution and human trafficking are, frankly, talking out of their ass. I've seen natural spikes in recorded incidents (because we assigned task forces to the problem) as 'proof' that the problem is increasing when in fact it may just be a matter of more resources leading to more discovery. For all we know, the total dark number has been dwindling.
Also consider that prostitution is just one subset of human trafficking - real world slavers won't stop their trade because demand for one service goes up or down. There will always be demand for human beings, the snakeheads don't care if their 'product' ends up in a brothel, restaurant, mansion, sweat shop or drug lab.
My humble suggestion is to stop hiding behind the human trafficking boogey man and just consider your own moral and practical stance on prostitution... because your laws for and against will NOT stop human trafficking as a crime and blight on humanity. For what it's worth, I do feel that legalizing prostitution makes 'regular' professionals more cooperative in pointing out excesses in their world to law enforcement (and the vast majority of arrests start with a cooperative witness so that's a big win.)