Two-thirds of the slaves were African born, and they tended to be less submissive than those born in the Americas and raised in slave societies. The death rate in the Caribbean exceeded the birth rate, so imports of enslaved Africans were necessary to maintain the numbers required to work the plantations. The slave population declined at an annual rate of two to five percent, due to overwork, inadequate food and shelter, insufficient clothing and medical care, and an imbalance between the sexes, with more men than women. Some slaves were of a creole elite class of urban slaves and domestics, who worked as cooks, personal servants and artisans around the plantation house. This relatively privileged class was chiefly born in the Americas, while the under-class born in Africa labored hard, and often under abusive and brutal conditions.