Michelle Goldberg in The Nation:
[D]efining “trafficking” can be politically fraught; there is a gray area between absolute exploitation and total free agency. “Most cases of trafficking are not the media-popular story of somebody being forcibly taken out of their home and forcibly chained to a bed,” says the Red Umbrella Fund’s van der Linde. “In my experience, most cases of trafficking are about women who were actually already working as a sex worker but decided to work somewhere else as a sex worker, and came into a situation where they faced some form of exploitation.”
However they ended up in the country, some women working as prostitutes in the Netherlands are being coerced. Majoor is no abolitionist, but her off-the-cuff estimate is even larger than that of the National Threat Assessment. “I think between 5 and 10 percent of sex workers are actually trafficked,” she says—which, given 20,000 prostitutes in the Netherlands, would mean somewhere between 1,000 and 2,000 people.
Academic evidence suggests that trafficking is exacerbated by legalization. A 2012 article by the scholars Seo-Young Cho, Axel Dreher and Eric Neumayer, published in the journal World Development, concluded that “countries with legalized prostitution have a statistically significantly larger reported incidence of human trafficking inflows. This holds true regardless of the model we use to estimate the equations and the variables we control for in the analysis.”
This can seem counterintuitive—shouldn’t legalization reduce the role of force in the industry, since it allows more women to enter sex work legally? The explanation, according to Cho, Dreher and Neumayer, is that while more women enter prostitution voluntarily in a legal market, the increase in the number of clients is even greater. Demand outstrips supply.