You mean like studies like "Some anti-prostitution activists have tried to claim that Germany’s liberal form of legalization has encouraged sex trafficking. But they actually cite coercion among illegal sex workers (for example, those who are too young to legally work at a German brothel)". (https://www.washingtonpost.com/news/the-watch/wp/2014/03/27/...)

Who would have guessed that those remaining in the illegal sector do not enjoy the benefit of decriminalization, almost like decriminalization create a bigger divide between what is legal and illegal. I would guess the same thing happened to smugglers after the prohibition, where those staying as a smuggler had to start transporting much more dangerous stuff like guns, explosives and heavy drugs. The lives of those smugglers surly got worse on the average, where the lives of those who went from illegal to legal got significant better. But let not look at those whose life got better since that would hurt the message of the study.