Construction of the Trans-Atlantic Slave Trade Database: Sources and Methods

Regions of Embarkation and Disembarkation

The above procedures generate imputed figures, where necessary, for the data used to produce series of slave departures and arrivals for eight different regions in Africa and sixty-four different regions of disembarkation. The variables “Total slaves embarked*” (SLAXIMP) and “Total slaves disembarked*” (SLAMIMP) incorporate these imputed data. “Total slaves embarked” is derived first from the data variable, “Total slaves embarked” (TSLAVESD). When values for this are not available, then a SLAXIMP value is derived from the sum of values available for “Slaves carried from first port of purchase” (NCAR13), “Slaves carried from second port of purchase” (NCAR15), and “Slaves carried from third port of purchase” (NCAR17)--in other words, the slaves embarked at up to three ports in Africa where these are available. If these data are incomplete or missing then SLAXIMP draws from the data variable “Number of slaves arriving at first place of landing” (SLAARRIV) adjusted for voyage mortality (imputed, if necessary), and finally, if this is not available then “Total slaves purchased” (TSLAVESP) – a variable available only in the downloadable database is used. Only if none of these data variables can provide adequate information, does SLAXIMP incorporate one of the imputed values in the Appendix table. Similarly SLAMIMP is derived first from SLAARRIV, then, if necessary, from the sum of “Number of slaves disembarked at first place of landing “ (SLAS32), “Number of slaves disembarked at second place of landing “ (SLAS36), and “Number of slaves disembarked at third place of landing “ (SLAS39) - in other words the slaves disembarked at up to three ports at the completion of the Middle Passage. All four of these are data variables. If these are blank, then SLAMIMP draws on TSLAVESD when available, adjusted for shipboard mortality (again, imputed, as necessary). As with SLAXIMP, SLAMIMP resorts to the imputed values in the Appendix table only when sources do not document the number of Africans who were disembarked.

Most users will probably prefer to use “Total slaves embarked*” and “Total slaves disembarked*” in their analyses, but they should be aware that captive numbers are to be found in four different variables each at embarkation (PLAC1TRA, PLAC2TRA, PLAC3TRA, MJBYPTIMP) and disembarkation (SLA1PORT, ADPSALE1, ADPSALE2, MJSLPTIMP). Eighty-seven percent of the slaving voyages documented at specific African ports embarked slaves at only one location. This bulk loading pattern was particularly pronounced in regions east of the Bight of Benin. The captains who traded at more than one African location usually did so along the coastline from Senegal to Ouidah (Whydah). Single-port slave-trading occurred even more often in the Americas. Ninety-five percent of the slaving voyages that anchored at specific New World markets discharged their human cargoes at one port. Nevertheless, users should note that information on partial cargoes and full cargoes are located in four different data variables, one containing the total arrived or departed and the other three reflecting purchases (or sales) in possibly three different places. The imputed variables “Total slaves embarked*” and “Total slaves disembarked*” are based only on the principal place of trade in Africa or principal place of disembarkation. A more refined assessment of numbers of captives boarded or discharged requires a search of all eight variables (four for the embarked, and four for disembarked).