John Oliver covered this on Last Week Tonight. tl;dw Cocoa is almost exclusively grown in Ghana and Cote d'Ivoire, two West African countries. Most of these farms are family run and there are millions of them. All the Cocoa they produce is purchased by a few companies who dictate price. Because they buy at such a low price, the only way these farms make money is if they force children in their families to work the farm for no compensation. Ie. Child slavery.