Given these appalling conditions, it's little wonder that the average life expectancy for a Brazilian slave on a sugar plantation in the late 18th century was 23 years. Things were slightly better in British sugar colonies like Barbados, and in the U.S., living and working conditions were better still. So relatively good that in fact, slave populations began increasing naturally, meaning that more slaves were born than died. 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.