This may sound like a good thing, but it is of course its own kind of evil, because it meant that slave owners were calculating that if they kept their slaves healthy enough, they would reproduce, and then the slave owners could steal and sell their children. Or use them to work their land, either way. Anyway, this explains why even though the percentage of slaves imported from Africa to the United States was relatively small, slaves and other people of African descent came to make up a significant portion of the U.S. population. The brutality of working conditions in Brazil, on the other hand, meant that slaves were never able to increase their population naturally, hence the continued need to import slaves into Brazil until slavery ended in the 1880s. So I noted earlier that slavery isn't new. It's also a hard word to define. Like Stalin forced millions to work in the gulags, but we don't usually consider those people slaves.