Working Paper
McGuirk E, Nunn N. Transhumant Pastoralism, Climate Change, and Conflict in Africa. Working Paper.Abstract
We consider the effects of climate change on seasonally migrant populations that herd livestock - i.e., transhumant pastoralists - in Africa. Traditionally, transhumant pastoralists benefit from a cooperative relationship with sedentary agriculturalists whereby arable land is used for crop farming in the wet season and animal grazing in the dry season. Droughts can disrupt this arrangement by inducing pastoral groups to migrate to agricultural lands before the harvest, causing conflict to emerge. We examine this hypothesis by combining ethnographic information on the traditional locations of transhumant pastoralists and sedentary agriculturalists with high-resolution data on the location and timing of rainfall and violent conflict events in Africa from 1989-2018. We show that droughts in the territory of transhumant pastoralists lead to conflict in neighboring areas. Consistent with the hypothesis, these conflict events are concentrated in agricultural areas; they occur during the wet season and not the dry season; and they are due to rainfall's impact on plant biomass growth. This mechanism explains a sizable proportion of conflict events in Africa, particularly civil conflicts and religious-extremist attacks. We find that the effects are muted in the presence of irrigation aid projects, but not in the presence of other forms of foreign aid. The effects approach zero as pastoral groups share more political power.
Nunn N. History as Evolution. Working Paper.Abstract
In this chapter, I consider the benefits of viewing history through an evolutionary lens. In recent decades, a field of research has emerged, which builds on foundations from biological evolution to study culture within an evolutionary framework. I begin the chapter by discussing the theory behind cultural evolution and the empirical evidence supporting its ability to explain the history of human societies. I then turn to a discussion of how an evolutionary perspective provides important insights into a range of phenomena within economics, including a deeper understanding of human capital, innovation, gender roles, the consequences of warfare, the effects of market competition, why we observe historical persistence and path dependence, and, most importantly, why sustained economic growth is often so elusive. I end by turning to a summary of a growing body of research within economics that has made progress in improving our understanding of cultural evolution and, thus, contributing to evolutionary disciplines outside of economics. 
Albright A, Cook J, Feigenbaum J, Kincaide L, Long J, Nunn N. After The Burning: The Economic Effects of the 1921 Tulsa Race Massacre. Working Paper.Abstract
The 1921 Tulsa Race Massacre resulted in the looting, burning, and leveling of 35 square blocks of a once-thriving Black neighborhood. Not only did this lead to severe economic loss, but the massacre also sent a warning to Black individuals across the country that similar events were possible in their communities. We examine the economic consequences of the massacre for Black populations in Tulsa and across the United States. We find that for the Black population of Tulsa, in the two decades that followed, the massacre led to declines in home ownership and occupational status. Outside of Tulsa, we find that the massacre also reduced home ownership. These effects were strongest in communities that were more exposed to newspaper coverage of the massacre or communities that, like Tulsa, had high levels of racial segregation. Examining effects after 1940, we find that the direct negative effects of the massacre on the home ownership of Black Tulsans, as well as the spillover effects working through newspaper coverage, persist and actually widen in the second half of the 20th Century.
Nunn N, Qian N, Wen J. Distrust and Political Turnover. Working Paper.Abstract

This paper documents an important channel through which culture can affect politics. Using an annual country-level panel that covers six decades, we show that economic downturns are more likely to cause political turnover in countries that have lower levels of generalized trust. The effect is strongest for turnovers occurring through regular procedures and during scheduled election years. The effect is much weaker and generally insignificant in non- democratic countries and for irregular turnovers such as military coups. We replicate our cross-country findings within the United States by looking at cross-county variation in trust, national recessions, and incumbent party vote-share in Presidential elections. Consistent with our cross-national findings, recessions cause a greater decline in the incumbent party vote share in counties with lower levels of generalized trust.


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.

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

We study the effects of Fair Trade (FT) certification of coffee on producers and households in Costa Rica. Examining the production dynamics of all Costa Rican coffee mills from 1999–2014, we find that when global coffee prices are lower and the FT guaranteed minimum price is binding, FT certification is associated with a higher sales price, greater sales, and more revenues. We also find that certification reduces the probability of a mill closing down and exiting the industry. Looking at households, we find that certification is associated with higher incomes for farm owners. Part of this is due to a transfer of incomes from intermediaries whose incomes decrease due to FT. We find no effect of FT on unskilled workers, who are the more disadvantaged group within the coffee  sector.

Web Article
Nunn N. Restraining Ourselves: Helping by Not Hurting. Economics for Inclusive Prosperity Policy Brief 19. 2020. Publisher's VersionAbstract
In this brief, I discuss the current state of economic development policy, which tends to focus on interventions, usually funded with foreign aid, that are aimed at fixing deficiencies in developing countries. The general perception is that there are inherent problems with less-developed countries that can be fixed by with the help of the Western world. I discuss evidence that shows that the effects of such ‘help’ can be mixed. While foreign aid can improve things, it can also make things worse. In addition, at the same time that this ‘help’ is being offered, the developed West regularly undertakes actions that are harmful to developing countries. Examples include tariffs, antidumping duties, restrictions on international labor mobility, the use of international power and coercion, and tied-aid used for export promotion. Overall, it is unclear whether interactions with the West are, on the whole, helpful or detrimental to developing countries. We may have our largest and most positive effects on alleviating global poverty if we focus on restraining ourselves from actively harming less-developed countries rather than focusing our efforts on fixing them.
Nunn N. Understanding the Long-Run Effects of Africa's Slave Trades. eBook: The Long Economic and Political Shadow of History, Volume 2. 2017. Publisher's VersionAbstract
Evidence suggests that Africa's slave trades played an important part in the shaping of the continent not only in terms of economic outcomes, but cultural and social outcomes as well. This column, taken from a recently published VoxEU eBook, summarises studies that reveal the lasting toxic effects of Africa’s four waves of slave trades on contemporary development.
PDF (full eBook)
Journal Article
Giuliano P, Nunn N. Understanding Cultural Persistence and Change. Review of Economic Studies. 2021; 88 (4) : 1541-1581.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 stable across generations, the traits that have evolved up to the previous generation are more likely to be suitable 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 climatic measures across 20-year generations from 500 to  1900. Employing a variety of tests that use different samples and empirical strategies, we find that populations with ancestors who lived in environments with more cross-generational instability place less importance on maintaining tradition today and exhibit less cultural persistence.

PDF Appendix
Nunn N. The Historical Roots of Economic Development. Science. 2020; 367 (6485) : eaaz9986.Abstract
This article reviews an emerging area of research within economics that seeks to better understand contemporary economic outcomes by taking a historical perspective. The field has established that many of the contemporary differences in comparative economic development have their roots in the distant past. The insights gained from this literature are not only of academic importance but also useful for thinking about policies that help to address global development moving forward. I provide examples of recent studies that have begun to take on this important next step in the literature by using insights gleaned from historical analyses to better understand policy and its optimal design.
Ashraf N, Bau N, Nunn N, Voena A. Bride Price and Female Education. Journal of Political Economy. 2020; 128 (2) : 591-641.Abstract
We document an important consequence of bride price, a payment made by the groom to the bride's family at marriage. Revisiting Indonesia's school construction program, we find that among ethnic groups without the custom, it had no effect on girls' schooling. Among ethnic groups with the custom, it had large positive effects. We show (theoretically and empirically) that this is because a daughter's education, by increasing the amount of money parents receive at marriage, generates an additional incentive for parents to educate their daughters. We replicate these findings in Zambia, a country that had a similar large-scale school construction program.
PDF Appendix
Moscona J, Nunn N, Robinson JA. Segmentary Lineage Organization and Conflict in Sub-Saharan Africa. Econometrica. 2020; 88 (5) : 1999-2036.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.

PDF Theoretical Note Supplementary Material Web Appendix
Sequeira S, Nunn N, Qian N. Immigrants and the Making of America. Review of Economic Studies. 2020; 87 (1) : 382-419.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 Slides Railway Shapefiles (15 years from 1830-1921)
Nunn N. Innis Lecture: Rethinking Economic Development. Canadian Journal of Economics. 2019; 52 (4) : 1349-1373.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?
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.

PDF Data
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.