I'm sorry, but I believe that considering human trafficking and prostitution solely from the perspective of economic inequality is a grave mistake. Whether prostitution involves females -- young girls, young women, or women of any age, or whether it involves males -- boys, young men, transvestites, or transsexuals -- men are essentially the ones using prostitutes. It is a social power relationship where men dominate; it isn't economic inequality.
One can explain the larger scale exploitation of Third World countries as regards prostitution on the basis of economic inequality, but prostitution or human trafficking is not a matter of economic inequality; it revolves around a power relationship between men and women and a deep social inequality between men and women. That clearly results in economic inequality, but to reduce human trafficking to nothing more than an economic issue associated with sex worker migration essentially ignores the fact that this fosters a system of male domination.