Ship Crowding and Slave Mortality: Missing Observations or Incorrect Measurement?

Abstract

Inconsistent measurement of ship tonnage, the denominator in the usual measures of crowded conditions on slave vessels, may confound estimated associations between crowding and slave mortality on the Middle Passage. The tonnages reported in Lloyd's Registers are shown to be consistent over time and are used to demonstrate that both the unstandardized and standardized tonnages in the Transatlantic Slave Trade Database are deeply flawed. Using corrected tonnages, we find that crowding increased mortality only on British slave ships and only before the passage of Dolben's Act in 1788.