Slavery is not only daily pain for humans but it is a national socio-economic defect that cause pile-up of different threats on several national and international levels. Such threats can and do cause long-term and large-scale barriers in secio-economic and socio-political structures. This is evident from the historical evolution of slavery (http://youtu.be/nHk-WceZeFg). It is interesting to see how developing countries suffered and still suffer from severe socio-economic disparities, and also mental health problems, from slavery. Slavery of yesterday still affect our ability to be successful today. There are interesting statistics, e.g. from the USA, that need to be taken into account (http://thyblackman.com/2015/02/15/the-slavery-card-fact-or-just-the-ultimate-excuse/).
Among important features of modern slavery are acceleration of different forms of gender and age discrimination and abuse of children (http://youtu.be/nNY2Vl8jUjU).