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

most impacted by the slave trades.
A second potential source of selection may be that societies that initially
had domestic slavery may have selected into the slave trades. If this is the
case, then the estimates may be capturing a negative relationship between
domestic slavery and subsequent economic development similar to that documented
by Engerman and Sokoloff (1997, 2002), Sokoloff and Engerman
(2000) and Lagerlöf (2005).
For the areas of Africa that were a part of the much older Islamic slave
trades there was domestic slavery. It is unclear whether domestic slavery
is a cause or a consequence of the external slave trades. However, for the
parts of Africa that were previously untouched by the Islamic trades, recent
evidence shows that prior to the trans-Atlantic slave trade, chattel slavery
did not exist. 19 Hilton (1985) shows that in West Central Africa there was
no trade in people prior to the arrival of the Portuguese. She provides
evidence showing that in the sixteenth century, words that originally meant
‘servant’ or ‘prisoner’, were altered to take on the meaning of a traded slave.
Historian and Anthropologist Jan Vansina (1989), using much more detailed
linguistic data, confirms Hilton’s finding that in West Central Africa there
was no word previously for slave. Vansina also maps the origin of the word
‘pika’ which originally meant servant, but took on the meaning of a traded
slave. The word originated at the coastal ports engaged in the slave trade
and spread to the inland communities that were also involved in the trade
(see Vansina, 1989, 1990). Additional studies from other regions also show
that prior to the external slave trade domestic slavery did not exist (e.g.,
Harms, 1981; Inikori, 2000; Hall, 2005, p. 16).
5.2 Instrumental Variables
There are two potential sources of bias in the OLS estimates. One arises
from the existence of country characteristics that are correlated with both
slave exports and current economic performance. The other is the presence
of classical and non-classical measurement error in the slave export estimates.
A potential solution to the two problems is the use of instrumental
variables. If one can find instruments that are correlated with slave exports,
but uncorrelated with country characteristics and measurement error, then
instrumental variables will yield consistent estimates. In the following two
sections, I provide IV estimates using two different instrumenting strategies.
19 Before this evidence was brought forth, there was debate in the literature over whether
domestic slavery existed prior to European arrival (e.g., Fage, 1962; Rodney, 1970).
27