Explaining the modern mortality decline: what can we learn from sea voyages

During the past two decades, scholars have attempted to quanify the mortality at sea of a large number of seaborne populations. We now have estimates of death rates associated with over 13,000 voyages between 1497 and the First World War. These include voyages of Portuguese and Dutch travellers to Asian destinations; African slaves, European convicts, and free emigrants to the Americas; British convicts to Australia; British government-assisted emigrants to South Africa and Australia; and African, Indian, Chinese, and Pacific Islander indentured labourers to various destinations in the Atlantic, Indian, and Pacific Ocean regions. Whereas the death rate on slave voyages did not decline over time, the death rate of young adults and older children on non-slave voyages plummeted in the early-to-middle nineteenth century, preceding the modern mortality decline on land. Yet, the infant death rate of babies who embarked, or who were born at sea, although steadily declining, remained very much higher than infant mortality on land. The reduction in infant maritime mortality, which lagged well behind that of voyaging adults and children, thus mirrors the difficulty in reducing infant death rates on land. This paper surveys the recent literature on mortality at sea, drawing implications for our understanding of the modern mortality decline on land.