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

USA; Havana, Cuba; Haiti; Kingston, Jamaica; Dominica; Martinique;
Guyana; Salvador, Brazil; and Rio de Janeiro, Brazil. 21
3. The sailing distance from the point on the country’s coast that is
closest to its centroid to the closest of the two major slave destinations
of the Indian Ocean slave trade: Mauritius and Muscat, Oman.
4. The overland distance from a country’s centroid to the closest port of
export for the trans-Saharan slave trade. The markets are: Algiers,
Tunis, Tripoli, Benghazi and Cairo.
5. The overland distance from a country’s centroid to the closest port of
export for the Red Sea slave trade. The ports are: Massawa, Suakin,
and Djibouti. 22
The distance instruments are also illustrated in Figure 7, which shows
the five distances for Burkina Faso. Also shown are the locations of demand
in each of the four slave trades. In the figure the ports and distance for
each of the slave trades is shown in a different color. Further details of the
construction of the instruments is given in the appendix.
Of the five instruments, there is particular concern that the distance
from a country’s interior to the coast is correlated with the error term in
the second stage. It has been shown that easy access to the coast allows
countries to more cheaply engage in international trade, which increases income
(see Rappaport and Sachs, 2003). In addition, distance to the coast is
correlated with the measurement error that results from the under-sampling
of slaves from the interior. Even though the distance to the coast is problematic
as an instrument, it is still useful to report the estimates with the
variable included as part of the instrument set. As I show in Section B of the
appendix, if the instrument is positively correlated with the measurement
error and/or negatively correlated with the error term in the second stage,
then the IV estimate will be biased towards zero. Therefore, the IV estimate
with distance to the coast in the instrument set is still useful because it can
be taken as a lower bound estimate of the effect of slave exports on income.
I also report estimates after eliminating the distance to the coast variable
from the instrument set.
21 Data on slave imports are from Eltis and Richardson (forthcoming). There is a significant
drop in the volume of slave imports between the 9th and 10th largest markets.
Because of this natural break, I use the top 9 markets.
22 For the island countries, one cannot reach the ports of the Saharan or Red Sea slave
trades by traveling overland. For these countries I use the sum of the sailing distance and
overland distance.
29