“Revealing the Relationship between Ship Crowding and Slave Mortality: The Role of Missing Data,” The Journal of Economic History 74(2):535-552, June 2014.
Historical accounts have linked the overcrowded conditions on the Middle Passage to slaves’ ill health and high mortality. A large literature in economic history has failed to find such effects. This note demonstrates the importance of a statistical explanation: missing data. Studies finding no positive relationship between vessel crowding and Middle Passage mortality are driven by an unrepresentative sample of slave voyages. Using simple methods to correct for missing data on voyage duration, analysis of the Trans-Atlantic Slave Trade Database shows a strong and robust association between crowded voyages and slave mortality, consistent with historical accounts.