Working Paper
Haushofer J, Lowes S, Musau A, Ndetei D, Nunn N, Poll M, Qian N. Stress, Ethnicity, and Prosocial Behavior. Working Paper.
Rossignol EL, Lowes S, Nunn N. Traditional Supernatural Beliefs and Prosocial Behavior. Working Paper.Abstract
In sub-Saharan Africa, traditional supernatural beliefs, including belief in witchcraft, black magic, or fetishism, are widespread. Some have hypothesized that these beliefs help to sustain cooperative behavior in a setting where the state is often absent. Others have documented that, at least at a macro-level, such beliefs are negatively associated with prosocial behavior. We contribute to a better understanding of the causal effects of these traditional supernatural beliefs by using lab-in-the-field experiments in the Democratic Republic of the Congo. Participants complete a range of experimental tasks where one player chooses whether to act in a prosocial manner towards another player. Participants are randomly assigned to another player that has either a strong or weak belief in witchcraft, and this information is known by the players. We find that participants act less prosocially towards randomly-assigned partners who believe more strongly in witchcraft. We also find that antisocial behavior is more socially acceptable and prosocial behavior less socially acceptable when playing with a partner who believes more strongly in witchcraft. Our findings suggest that the negative relationship between witchcraft and prosocial outcomes observed in the data may, in fact, be due to the causal effect of the presence of traditional supernatural beliefs on people’s behavior.
Cao Y, Enke B, Falk A, Giuliano P, Nunn N. Herding, Warfare, and a Culture of Honor: Global Evidence. Working Paper.Abstract
According to the widely known ‘culture of honor’ hypothesis from social psychology, traditional herding practices are believed to have generated a value system that is conducive to revenge-taking and violence. We test this idea at a global scale using a combination of ethnographic records, historical folklore information, global data on contemporary conflict events, and largescale surveys. The data show systematic links between traditional herding practices and a culture of honor. First, the culture of pre-industrial societies that relied on animal herding emphasizes violence, punishment, and revenge-taking. Second, contemporary ethnolinguistic groups that historically subsisted more strongly on herding have more frequent and severe conflict today. Third, the contemporary descendants of herders report being more willing to take revenge and punish unfair behavior in the globally representative Global Preferences Survey. In all, the evidence supports the idea that this form of economic subsistence generated a functional psychology that has persisted until today and plays a role in shaping conflict across the globe.
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 find that droughts in the territory of transhumant pastoralists lead to conflict in neighboring areas. Consistent with the proposed mechanism, the effects 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. Since pastoralists tend to be Muslim and agriculturalists Christian, this mechanism accounts for a sizable proportion of the rapid rise in religious conflict observed in recent decades. Turning to policy responses, we find that development aid projects tend not to mitigate the effects that we document. By contrast, the effects are closer to zero when transhumant pastoralists have greater power in national government, suggesting that more equal political representation is conducive to peace.
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.

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
Nunn N. On the Dynamics of Human Behavior: The Past, Present, and Future of Culture, Conflict, and Cooperation. American Economic Review Papers and Proceedings. Forthcoming.Abstract
I provide a theoretically-guided discussion of the dynamics of human behavior, focusing on the importance of culture (socially-learned information) and tradition (transmission of culture across generations). Decision-making that relies on tradition can be an effective strategy and arises in equilibrium. While dynamically optimal, it generates static ‘mismatch.’ When the world changes, since traits evolve slowly, they may not be beneficial in their new environment. I discuss how mismatch helps explain the world around us, presents special challenges and opportunities for policy, and provides important lessons for our future as a human species.
Dragusanu R, Montero E, Nunn N. The Effects of Fair Trade Certification: Evidence from Coffee Producers in Costa Rica. Journal of the European Economic Association. Forthcoming.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.
PDF Appendix
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.

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