Working Paper
Nunn N, Qian N, Wen J. Distrust and Political Turnover. Working Paper.Abstract

We present findings that document one way in which a society’s culture can affect political outcomes. Examining an annual panel of democratic countries over six decades, we show that severe economic downturns are more likely to cause political turnover in countries that have lower levels of generalized trust. We find no such relationship in non-democratic countries or on irregular leader turnover. This pattern is consistent with a mechanism that works through accountability and the electoral process. As further corroboration of this mechanism, we find that the effects of trust are greatest during years with regularly-scheduled elections and within democracies with a parliamentary system, a fully free media, and more stability. The estimates suggest that generalized trust significantly affects political institutions by influencing the extent to which citizens attribute economic downturns to the mistakes of politicians.


Iyigun M, Nunn N, Qian N. The Long-Run Effects of Agricultural Productivity on Conflict, 1400-1900. Working Paper.Abstract

This paper provides evidence of the long-run effects of a permanent increase in agricultural productivity on conflict. We construct a newly digitized and geo-referenced dataset of battles in Europe, the Near East and North Africa covering the period between 1400 and 1900 CE. For variation in permanent improvements in agricultural productivity, we exploit the introduction of potatoes from the Americas to the Old World after the Columbian Exchange. We find that the introduction of potatoes permanently reduced conflict for roughly two centuries. The results are driven by a reduction in civil conflicts.

Moscona J, Nunn N, Robinson JA. Kinship and Conflict: Evidence from Segmentary Lineage Societies in Sub-Saharan Africa. Working Paper.Abstract

We test the long-standing hypothesis that ethnic groups that are organized around `segmentary lineages' are more prone to conflict. Ethnographic accounts suggest that in segmentary lineage societies, which are characterized by strong allegiances to distant relatives, individuals are obligated to come to the aid of fellow lineage members when they become involved in conflicts. As a consequence, small disagreements often escalate to larger-scale conflicts involving many individuals. We test for this link between segmentary lineage and conflict across 145 African ethnic groups in sub-Saharan Africa. Using a number of estimation strategies, including an RD design at ethnic boundaries, we find that segmentary lineage societies experience more conflicts and particularly ones that are retaliatory, long in duration, and large in scale.

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Giuliano P, Nunn N. Understanding Cultural Persistence and Change. Working Paper.Abstract

We examine a determinant of cultural persistence that has emerged from a class of models in evolutionary anthropology: the similarity of the environment across generations. Within these models, when the environment is more similar across generations, the traits that have evolved up to the previous generation are more likely to be optimal for the current generation. In equilibrium, a greater value is placed on tradition and there is greater cultural persistence. We test this hypothesis by measuring the variability of different climatic measures across 20-year generations from 500-1900. Employing a variety of tests, each using different samples and empirical strategies, we find that populations with ancestors who lived in environments with more cross-generational instability place less importance in maintaining tradition today and exhibit less cultural persistence.

PDF Appendix
Dragusanu R, Nunn N. The Effects of Fair Trade Certification: Evidence From Coffee Producers in Costa Rica. Working Paper.Abstract

We examine the effects of Fair Trade (FT) certification of coffee on producers and households in Costa Rica. Examining the production dynamics of the universe of Costa Rican coffee mills from 1999-2014, we find that FT certification is associated with a higher sales price, greater sales, and more revenues. As expected, these effects are greater when global coffee prices are lower and the FT guaranteed minimum price is binding. Looking at households, we find evidence that FT is associated with higher incomes for all families, but especially for those working in the coffee sector. However, we also find that, within this sector, the benefits are not evenly distributed. Farm owners and skilled workers benefit from FT, intermediaries are hurt, and hired unskilled workers are unaffected. Thus, although FT creates sizable benefits (on average), it also results in a redistribution from intermediaries to farmers. Lastly, we also find evidence of positive effects of FT certification on the education of high-school-aged children, which is most likely due to the presence of scholarship programs that are funded by FT premiums.

Journal Article
Nunn N. Rethinking Economic Development. Canadian Journal of Economics. Forthcoming.Abstract
I provide a summary, reflection, and assessment of the current state of economic development in both the policy and academic worlds. In terms of development policy, currently, the primary focus is on policy interventions, namely, foreign aid, aimed at fixing the `deficiencies' of developing countries. Academic research also has a similar focus, except with an emphasis in rigorous evaluation of interventions to estimate causal effects. A standard set of versatile quantitative tools is used, e.g., experimental and quasi-experimental methods, which can be easily applied in a range of settings to estimate the causal effects of policies, which are typically presumed to be similar across contexts. In this article, I take a step back and ask whether the current practices are the best that we can do. Are foreign aid and policy interventions the best options we have for poverty alleviation? What else can be done? Is our current research strategy, characterized by rigorous but a lack of context-specific analysis,  the best method of analysis? Is there a role for other research methods, for a deeper understanding of the local context and for more collaboration with local scholars?
Ashraf N, Bau N, Nunn N, Voena A. Bride Price and Female Education. Journal of Political Economy. Forthcoming.Abstract
This study contributes to our understanding of the importance of cultural context for development policy. We show how the success of education policies depends on a widely-practiced marriage custom called bride price, which is a payment made by the husband to the wife's parents at marriage. We begin by developing a model of parental investment in children's education when there is a bride price. The model generates a number of predictions that we test in two countries -- Indonesia and Zambia -- that had large-scale school construction projects. Consistent with the model, we find that the amount of bride price received by the parents is increasing in their daughter's education. As a consequence, among bride price ethnic groups, female educational attainment is higher, and female education is more responsive to the school construction programs. In fact, we find that the programs had no discernible effect on the education of girls from non-bride price groups, but had large positive effects for girls from bride price groups. Thus, the success of the programs depended critically on the marriage custom.
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Sequeira S, Nunn N, Qian N. Immigrants and the Making of America. Review of Economic Studies. Forthcoming.Abstract

We study the effects of European immigration to the United States during the Age of Mass Migration (1850-1920) on economic prosperity. Exploiting variation in the extent of immigration across counties arising from the interaction of fluctuations in aggregate immigrant flows and the gradual expansion of the railway network, we find that counties with more historical immigration have higher incomes, less poverty, less unemployment, higher rates of urbanization, and greater educational attainment today. The long-run effects appear to arise from the persistence of sizeable short-run benefits, including greater industrialization, increased agricultural productivity, and more innovation.

PDF Appendix Railway Shapefiles (15 years from 1830-1921)
van Dorp L, Lowes S, Weigel JL, Ansari-Pour N, Lopez S, Mendoza-Revilla J, Robinson JA, Henrich J, Thomas MG, Nunn N, et al. Genetic Legacy of State Centralization in the Kuba Kingdom of the Democratic Republic of the Congo. Proceedings of the National Academy of Sciences (PNAS). 2019; 116 (2) : 593-598.Abstract
Few phenomena have had as profound or long-lasting consequences in human history as the emergence of large-scale centralized states in the place of smaller-scale and more local societies. This study examines a fundamental, and yet unexplored, consequence of state formation: its genetic legacy. We study the genetic impact of state centralization during the formation of the eminent precolonial Kuba Kingdom of the Democratic Republic of the Congo (DRC) in the 17th century. We analyze genome-wide data from over 690 individuals sampled from 27 different ethnic groups from the Kasai Central Province of the DRC. By comparing genetic patterns in the present-day Kuba, whose ancestors were part of the Kuba Kingdom, with those in neighboring non-Kuba groups, we show that the Kuba today are more genetically diverse and more similar to other groups in the region than expected, consistent with the historical unification of distinct subgroups during state centralization. We also find evidence of genetic mixing dating to the time of the Kingdom at its most prominent. Taken together, our findings show the power of genetics to better understand the behaviors of both people and institutions in the past.
PDF Supplementary Materials PNAS Commentary
Alesina A, Giuliano P, Nunn N. Traditional Agricultural Practices and the Sex Ratio Today. PLoS ONE. 2018; 13 (1) : e0190510.Abstract
We study the historical origins of cross-country differences in the male-to-female sex ratio. Our analysis focuses on the use of the plough in traditional agriculture. In societies that did not use the plough, women tended to participate in agriculture as actively as men. By contrast, in societies that used the plough, men specialized in agricultural work, due to the physical strength needed to pull the plough or control the animal that pulls it. We hypothesize that this difference caused plough-using societies to value boys more than girls. Today, this belief is reflected in male-biased sex ratios, which arise due to sex-selective abortion or infanticide, or gender-differences in access to family resources, which results in higher mortality rates for girls. Testing this hypothesis, we show that descendants of societies that traditionally practiced plough agriculture today have higher average male-to-female sex ratios. We find that this effect systematically increases in magnitude and statistical significance as one looks at older cohorts. Estimates using instrumental variables confirm our findings from multivariate OLS analysis.
PDF Supplementary Material
Giuliano P, Nunn N. Ancestral Characteristics of Modern Populations. Economic History of Developing Regions. 2018; 33 (1) : 1-17.Abstract

We construct a database, with global coverage, that provides measures of the cultural and environmental characteristics of the pre-industrial ancestors of the world's current populations. In this paper, we describe the construction of the database, including the underlying data, the procedure to produce the estimates, and the structure of the final data. We then provide illustrations of some of the variation in the data and provide an illustration of how the data can be used.

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Lowes S, Nunn N, Robinson JA, Weigel J. The Evolution of Culture and Institutions: Evidence from the Kuba Kingdom. Econometrica. 2017; 85 (4) : 1065-1091.Abstract

We use variation in historical state centralization to examine the long-term impact of institutions on cultural norms. The Kuba Kingdom, established in Central Africa in the early 17th century by King Shyaam, had more developed state institutions than the other independent villages and chieftaincies in the region. It had an unwritten constitution, separation of political powers, a judicial system with courts and juries, a police force, a military, taxation, and significant public goods provision. Comparing individuals from the Kuba Kingdom  to those from just outside the Kingdom, we find that centralized formal institutions are associated with weaker norms of rule following and a greater propensity to cheat for material gain. This finding is consistent with recent models where endogenous investments to inculcate values in children decline when there is an increase in the effectiveness of formal institutions that enforce socially desirable behavior. Consistent with such a mechanism, we find that Kuba parents believe it is less important to teach children values related to rule-following behaviors.

PDF Supplementary Materials Extended Appendix Protocols
Moscona J, Nunn N, Robinson JA. Keeping It in the Family: Lineage Organization and the Scope of Trust in Sub-Saharan Africa. American Economic Review Papers and Proceedings. 2017; 107 (5) : 565-571.Abstract

We present evidence that the traditional structure of society is an important determinant of the scope of trust today. Within Africa, individuals belonging to ethnic groups that organized society using segmentary lineages exhibit a more limited scope of trust, measured by the gap between trust in relatives and trust in non-relatives. This trust gap arises because of lower levels of trust in non-relatives and not higher levels of trust in relatives. A causal interpretation of these correlations is supported by the fact that the effects are primarily found in rural areas where these forms of organization are still prevalent.

Nunn N, de la Sierra RS. Why Being Wrong can be Right: Magical Warfare Technologies and the Persistence of False Beliefs. American Economic Review Papers and Proceedings. 2017; 107 (5) : 582-587.Abstract

Across human societies, one sees many examples of deeply rooted and widely-held beliefs that are almost certainly untrue. Examples include beliefs about witchcraft, magic, ordeals, and superstitions. Why are such incorrect beliefs so prevalent and how do they persist? We consider this question through an examination of superstitions and magic associated with conflict in the Eastern Democratic Republic of the Congo. Focusing on superstitions related to bullet-proofing, we provide theory and case-study evidence showing how these incorrect beliefs persist. Although harmful at the individual-level, we show that they generate Pareto efficient outcomes that have group-level benefits.

Lowes S, Nunn N, Robinson JA, Weigel J. Understanding Ethnic Identity in Africa: Evidence from the Implicit Association Test (IAT). American Economic Review Papers and Proceedings. 2015; 105 (5) : 340-345.Abstract

We use a variant of the Implicit Association Test (IAT) to examine individuals’ implicit attitudes towards various ethnic groups. Using a population from the Democratic Republic of Congo, we find that the IAT measures show evidence of an implicit bias in favor of one’s own ethnicity. Individuals have implicit views of their own ethnic group that are more positive than their implicit views of other ethnic groups. We find this implicit bias to be quantitatively smaller than the (explicit) bias one finds when using self-reported attitudes about different ethnic groups.

PDF Appendix IAT program files
Dragusanu R, Giovannucci D, Nunn N. The Economics of Fair Trade. Journal of Economic Perspectives. 2014; 28 (3) : 217-236.Abstract

Fair Trade is a labeling initiative aimed at improving the lives of the poor in developing countries by offering better terms to producers and helping them to organize. Whether Fair Trade can achieve its intended goals has been hotly debated in academic and policy circles. In particular, debates have been waged about whether Fair Trade makes "economic sense" and is sustainable in the long run. The aim of this article is to provide a critical overview of the economic theory behind Fair Trade, describing the potential benefits and potential pitfalls. We also provide an assessment of the empirical evidence of the impacts of Fair Trade to date.

Nunn N, Qian N. U.S. Food Aid and Civil Conflict. American Economic Review. 2014; 104 (6) : 1630-1666.Abstract

We study the effect of U.S. food aid on conflict in recipient countries. Our analysis exploits time variation in food aid shipments due to changes in U.S. wheat production and cross-sectional variation in a country's tendency to receive any U.S. food aid. According to our estimates, an increase in U.S. food aid increases the incidence and duration of civil conflicts, but has no robust effect on inter-state conflicts or the onset of civil conflicts. We also provide suggestive evidence that the effects are most pronounced in countries with a recent history of civil conflict.

PDF Appendix
Giuliano P, Nunn N. The Transmission of Democracy: From the Village to the Nation-State. American Economic Review Papers and Proceedings. 2013; 103 (3) : 86-92.Abstract

We provide evidence that a history of democracy at the local level is associated with contemporary democracy at the national level. Auxiliary estimates show that a tradition of local democracy is also associated with attitudes that favor democracy, with better quality institutions, and higher level of economic development.

Nunn N, Trefler D. Incomplete Contracts and the Boundaries of the Multinational Firm. Journal of Economic Behavior & Organization. 2013; 94 (1) : 330-344.Abstract
Using data on U.S. intra-firm and arm’s-length imports for 5,705 products imported from 220 countries, we examine the determinants of the share of U.S. imports that are intra-firm. We examine two predictions that arise from Antràs (2003), Antràs & Helpman (2008) and Antràs & Helpman (2004). First, we find that, consistent with the implicit logic of Antràs (2003) and the explicit predictions of Antràs & Helpman (2008), vertical integration is increasing in the importance of non-contractible headquarter inputs relative to non-contractible supplier inputs. In other words, we show that only non-contractible headquarter inputs affect the firm’s make-or-buy decision. Second, we also provide empirical support for the Antràs & Helpman (2004) prediction that intra-firm trade is largest where non-contractible headquarter inputs are important and productivity is high.
Berger D, Easterly W, Nunn N, Satyanath S. Commercial Imperialism? Political Influence and Trade During the Cold War. American Economic Review. 2013; 103 (2) : 863-896.Abstract

We exploit the recent declassification of CIA documents and examine whether there is evidence of US power being used to influence countries’ decisions regarding international trade. We measure US influence using a newly constructed annual panel of CIA interventions that were successful at installing and supporting leaders during the Cold War. Our presumption is that the US had greater influence over foreign leaders that were installed and backed by the CIA. We show that following successful CIA interventions there was an increase in foreign-country imports from the US, but there was no similar increase in foreign-country exports to the US. Further, the increase in US exports was concentrated in industries which the US had a comparative disadvantage in producing, not a comparative advantage. This is consistent with US influence being used to create a larger foreign market for American products. Our analysis is able to rule out decreased bilateral trade costs, changing political ideology, and an increased supply of US loans and grants as alternative explanations. We provide evidence that the increase in US exports arose through direct purchases of US products by foreign governments.

PDF Appendix Slides