The Long-Term Effects of Africa's Slave TradesNunn, Nathan (2007): The Long-Term Effects of Africa's Slave Trades. Forthcoming in: Quarterly Journal of EconomicsAbstractCan part of Africa’s current underdevelopment be explained by its slave trades? To explore this question, I use data from shipping records and historical documents reporting slave ethnicities to construct estimates of the number of slaves exported from each country during Africa’s slave trades. I find a robust negative relationship between the number of slaves exported from a country and current economic performance. To better understand if the relationship is causal, I examine the historical evidence on selection into the slave trades, and use instrumental variables. Together the evidence suggests that the slave trades have had an adverse effect on economic development.



VI. Possible Channels of CausalityI now turn to the channels through which the slave trades may have
affected economic development. I view this analysis as preliminary and ex-
ploratory. With only 52 observations it is not possible to pin down the pre-
cise channels and mechanism underlying the relationships with any reason-
able degree of certainty. My strategy here is to simply investigate whether
the data are consistent with the historic events described Section II.
An important consequence of the slave trades was that they tended to
weaken ties between villages, thus discouraging the formation of larger com-
munities and broader ethnic identities. I explore whether the data are consis-
tent with this channel by examining the relationship between slave exports
and a measure of current ethnic fractionalization from Alesina et al. [2003].
As shown in Figure VI, there is a strong positive relationship between the
two variables.18 This is consistent with the historic accounts of the slave
trades impeding the formation of broader ethnic identities.
This consequence of the slave trades is important because of the increas-
ing evidence showing that ethnic fractionalization is an important deter-
minant of a variety of factors necessary for economic development. Since
the seminal article documenting the link between ethnic diversity and eco-
nomic growth by Easterly and Levine [1997], subsequent research by La
Porta et al. [1999], Alesina et al. [2003], Aghion et al. [2004], and Easterly
et al. [2006] looks more deeply into why ethnic fractionalization is important
for development. These studies find that ethnic diversity is important for
social cohesion, domestic institutions, domestic polices, and the quality of
government. As well, Alesina et al. [1999], Miguel and Gugerty [2005], and
Banerjee and Somanathan [2006] find that ethnic fractionalization reduces
the provision of public goods, such as education, health facilities, access
to water, and transportation infrastructure, all of which are important for
economic development.
A second, and closely related, consequence of the slave trades was the
weakening and underdevelopment of states. To examine whether the data
are consistent with this channel, I consider the relationship between slave ex-
ports and the level of state development following the slave trades. To do this
I use a measure of pre-colonial state development from Gennaioli and Rainer
[2006]. The measure is constructed using ethnographic data from Murdock
[1967] on the indigenous political complexity of ethnic groups, measured by

the number of jurisdictional hierarchies beyond the local community. The
original measure ranges from 0 to 4, with 0 indicating “stateless” societies
and 4 indicating societies with “large states” [Murdock, 1967, p. 52]. Using
this data, Gennaioli and Rainer [2006] construct a measure of the proportion
of a country’s indigenous population that belongs to an ethnic group that
falls into category 2, 3, or 4.
The relationship between slave exports and 19th century state devel-
opment is shown in Figure VII. The negative relationship between slave
exports and state centralization shown in the figure is consistent with the
historic accounts of the slave trades causing long-term political instability,
which resulted in weakened and fragmented states.
Recent empirical research shows that a country’s history of state de-
velopment is an important determinant of current economic performance.
Bockstette et al. [2002] and Chanda and Putterman [2005] find that ‘state
antiquity’, measured using an index of the depth of experience with state-
level institutions, is positively correlated with real per capita GDP growth
between 1960 and 1995. Looking within Africa, Gennaioli and Rainer [2006]
find that countries with ethnicities that had centralized pre-colonial state
institutions today provide more public goods, such as education, health, and infrastructure.

Herbst [1997, 2000] also focuses on the importance of state development
for economic success, arguing that Africa’s poor economic performance is a
result of post-colonial state failure, the roots of which lie in the underde-
velopment and instability of pre-colonial polities. Herbst [2000, chpt. 2–4]
argues that because of a lack of significant political development during
colonial rule, the limited pre-colonial political structures continued to exist
after independence.19 As a result, Africa’s post-independence leaders inher-
ited nation states that did not have the infrastructure necessary to extend
authority and control over the whole country. Many states were, and still
are, unable to collect taxes from its citizens, and as a result they are also
unable to provide a minimum level of public goods and services.
A corollary of Herbst’s argument is that the impact of the slave trades
may have been felt most strongly after colonial independence. This is be-
cause this is when pre-colonial political structures suddenly increased in im-
portance, as they became central determinants of the success of the newly
formed state. Using Figure VIII, I examine whether the evolution of in-
comes since 1950 is consistent with this hypothesis. The figure shows av-
erage per capita GDP between 1950 and 2000 for two groups of African
countries.20 One group consists of the 26 countries with the lowest mea-
sures of ln(exports/area) and the other is the 26 countries with the highest
measures of ln(exports/area). As shown in the figure, throughout the pe-
riod low slave export countries are richer on average than high slave export
countries. Also interesting, however, is the difference in the evolution of
income between the two groups of countries. Although the low slave export
countries were richer in the early 1950s when most countries were still under
colonial rule, the income gap between the two groups increased significantly
over time, and became most pronounced after the late 1960s and early 1970s
when most countries had gained independence.21 This pattern is consistent
with the slave trades affecting early state development, which may have
mattered during colonial rule, but mattered much more after independence.
Because those parts of Africa that were most severely impacted by the slave
trades tended to have the least developed political systems, after indepen-
dence these countries continued to have weak and unstable states, as well
as slower economic growth.
VII. ConclusionsCombining data from shipping records and data from historical docu-
ments reporting slave ethnicities, I have constructed estimates of the num-
ber of slaves exported from each country in Africa during Africa’s four slave
trades. I found a robust negative relationship between the number of slaves
taken from a country and its subsequent economic development.
I pursued a number of strategies to better understand if the relation-
ship is causal or spurious. If countries that were initially underdeveloped
selected into the slave trades, and if these countries continue to be under-
developed today, then this may explain the observed relationship between
slave exports and current income. I first reviewed the historical evidence on
the characteristics of African societies that were most affected by the slave
trades. The qualitative and quantitative evidence show that it was actually
the most developed parts of Africa, not the least developed, that tended
to select into the slave trades. I also used the distances from each country
to the locations of the demand for slaves as instruments to estimate the
causal effect of the slave trades on economic development. The IV estimates
confirmed the OLS results, suggesting that increased extraction during the
slave trades resulted in worse economic performance.
I then examined the channels of causality underlying the relationship
between slave exports and economic development. I showed that the data are
consistent with historic accounts suggesting that the slave trades impeded
the formation of broader ethnic groups, leading to ethnic fractionalization,
and that the slave trades resulted in a weakening and underdevelopment of
political structures.
http://mpra.ub.uni-muenchen.de/4134/1/MPRA_paper_4134.pdf