Slavery would have become untenable anyway. Imagine the costs required to provide food and accomodation for a group of slaves in America in the modern day, let alone transporting them. Even at a low standard it would be unrealistic. That's why work is outsourced to other countries now where people can be used to work for incredibly low wages due to low living costs in particular countries. Added bonus is you don't need to worry about worker's health or work conditions because it doesn't mean any downturn in production. It's worse than slavery in many ways but since it's not called slavery we all seem okay with it.
[Blinking eyes thing]
Steam: http://steamcommunity.com/id/tzyon
Steam: http://steamcommunity.com/id/tzyon