The labour for these plantations was provided by an estimated 790,000 African slaves (accounting in 1783–1791 for a third of the entire Atlantic slave trade). Between 1764 and 1771, the average annual importation of slaves varied between 10,000-15,000; by 1786 it was about 28,000, and from 1787 onward, the colony received more than 40,000 slaves a year. However, the inability to maintain slave numbers without constant resupply from Africa meant the slave population in 1789 totalled 500,000, ruled over by a white population that numbered only 32,000.