The Long-Term Effects of Africa's Slave Trades - Social Sciences ...

3 Slave Export Data
3.1 Construction of Estimates
In this section I provide an overview of the data sources and methodology
used to construct the slave export figures. Full details of the data construction
are in Nunn (2006a). 11
To construct the slave export estimates, I rely on two types of data.
The first are data that report the total number of slaves exported from each
port or region in Africa. I refer to these data as shipping data. For the
trans-Atlantic slave trade, the data are from the updated version of the
Trans-Atlantic Slave Trade Database constructed by Eltis et al. (1999). 12
The database records 34,584 voyages from 1514 to 1866. The shipping data
are originally from various documents and records located around the world.
In most European ports, merchants were required to register their ships,
declare the volume and value of goods transported, pay duties, and obtain
formal permission to leave the port. Therefore, for each ship and voyage,
typically, there exists a number of different registers and documents. As
well, shipping news and information published in newspapers and periodicals
provide additional sources of information. In the database, 77% of the trans-
Atlantic slave voyages after 1700 have shipping information from more than
one source. Voyages are documented in as many as sixteen different sources
and the average number of sources of data for each voyage is six. According
to the authors’ estimates, the database contains 82% of all trans-Atlantic
slaving voyages ever attempted (Eltis and Richardson, forthcoming).
Data for the early period of the Atlantic slave trade not covered by the
Trans-Atlantic Slave Trade Database are from Elbl (1997). For the Indian
Ocean, Red Sea and trans-Saharan slave trades data are from Austen (1979),
Austen (1988), and Austen (1992). The data from these sources are based on
estimates from all available documents, records and accounts by observers
and government officials on the location and volume of slaves exports.
With the shipping data one can calculate the number of slaves that were
shipped from each country. However, the data do not provide a reliable
11 The estimates only quantify Africa’s external slave trades, and therefore do not include
slaves that entered into domestic slavery. Because of a lack of data on the numbers and
origins of domestic slaves, I am unable to include these slaves in my estimates.
12 In Nunn (2004), I used the original version of the database. The new edition represents
a significant improvement in the quality and completeness of the data. The updated
database includes the records of 8,005 new voyages and adds additional information for
18,000 pre-existing voyages. In particular, the new database has 75% more information
on the slaves’ ports of embarkation (see Eltis and Richardson, forthcoming).
11