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Construction of the Trans-Atlantic Slave Trade Database: Sources and Methods
David Eltis
(Emory University),
2010
Data Variables
The variables include information that, for convenience, have been grouped into eight categories: (1) vessel characteristics
(name, tonnage, rig, guns, place and year of construction, owners); (2) the outcome of the voyage (3) the itinerary of the voyage;
(4) the dates at which the vessel left or arrived; (5) the captain and crew of the vessel; (6) the numbers of captives; (7) the
characteristics of the captives and their experience of mortality; and (8) the sources for the record. The Variable List in the
“Understanding the Database” section presents a complete listing of the data variables as well as the imputed variables in the
data set. Imputed variables are always marked with an asterisk. No voyage, however, includes information for all data or imputed
variables. Table 1 provides a summary of the coverage for some of the more important data variables.
Generally, we attempted to preserve the written documentary record in adding to the data variables. Numeric variables, such
as vessel tonnage, numbers of crew, and numbers of slaves, demanded a ranking of sources, particularly for the well-documented
British trade. (5)
Table 1. Select Summary of Information Contained in the Trans-Atlantic Slave Voyage Data Set: Version 2008 Compared to 2010
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2008 |
2010 |
| Number of slave voyages in the data set |
34,940 |
34,948 |
| Voyages with name of vessel |
33,337 |
33,353 |
| Voyages with name of captain(s) |
30,895 |
30,894 |
| Voyages with name of at least one ship owner |
21,024 |
21,064 |
| Tonnage of ship available |
17,691 |
17,608 |
| Place of ship departure given |
28,443 |
28,449 |
| Date of ship departure given |
22,193 |
22,231 |
| Place(s) of embarkation on the African coast available |
21,121 |
21,291 |
| Numbers of Africans embarked reported |
8,207 |
8,272 |
| Voyages with age or gender of Africans reported |
4,426 |
4,498 |
| Place(s) of disembarkation available |
24,849 |
24,916 |
| Dates of arrival at place of disembarkation available |
17,446 |
17,533 |
| Numbers of Africans disembarked reported |
18,184 |
18,269 |
| Voyages reporting number of Africans died on board |
6,332 |
6,438 |
| Voyages with place of ship construction reported |
8,881 |
8,888 |
| Date of return to Europe or end of voyage given |
10,100 |
10,414 |
| Some indication of outcome of voyage indicated |
31,554 |
31,612 |
Sources often report different numbers of slaves embarked on or "taken on board" the coast of Africa or landed in the
Americas. Furthermore, for some years there are inconsistencies in slave age or gender totals per voyage. Regarding
slave exports, we were careful to distinguish between the number of slaves purchased and the number who in fact were
shipped from the coast. We used slave departure totals, whether reported by slave traders, African merchants, or
European captains, agents, or merchants. We included the slave departures reported in sources such as logs kept by
the Dutch and English castles on the Gold Coast, even though the totals often were rounded numbers, such as 400 or
500 slaves, and even though the totals occasionally were significantly less than the numbers of slaves who were disembarked
in the Americas. Users should keep these biases in mind, not least for any calculations of mortality they may wish to try.
For slave arrivals recorded in customs documents or shipping gazettes, we decided to use maximum totals where there was
conflicting information, under the assumption that these differences might indicate deaths of slaves before slaves disembarked.
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