 Mortality of around 20%, a number similar and sometimes greater than those of the slaves, was expected in a ship's crew during the course of a voyage; this was due to disease, flogging, overwork, or slave uprisings.Disease (malaria or yellow fever) was the most common cause of death among sailors.A high crew mortality rate on the return voyage was in the captain's interests as it reduced the number of sailors who had to be paid on reaching the home port.