Suppose X and Y are binary exposure and outcome variables, and we have full knowledge of the distribution of Y, given application of X. We are interested in assessing whether an outcome in some case is due to the exposure. This “probability of causation” is of interest in comparative historical analysis where scholars use process tracing approaches to learn about causes of outcomes for single units by observing events along a causal path. The probability of causation is typically not identified, but bounds can be placed on it. Here, we provide a full characterization of the bounds that can be achieved in the ideal case that X and Y are connected by a causal chain of complete mediators, and we know the probabilistic structure of the full chain. Our results are largely negative. We show that, even in these very favorable conditions, the gains from positive evidence on mediators is modest.
Public support for global vaccine sharing in the COVID-19 pandemic: Evidence from Germany
Ferdinand Geissler, Felix Hartmann, Macartan Humphreys, Heike Klüver, and 1 more author
By September 2021 an estimated 32% of the global population was fully vaccinated for COVID-19 but the global distribution of vaccines was extremely unequal, with 72% or more vaccinated in the ten countries with the highest vaccination rates and less than 2% in the ten countries with the lowest vaccination rates. Given that governments need to secure public support for investments in global vaccine sharing, it is important to understand the levels and drivers of public support for international vaccine solidarity. Using a factorial experiment administered to more than 10,000 online survey respondents in Germany in 2021, we demonstrate that the majority of German citizens are against global inequalities in vaccine distribution. Respondents are supportive of substantive funding amounts, on the order of the most generous contributions provided to date, though still below amounts that are likely needed for a successful global campaign. Public preferences appear largely to be driven by intrinsic concern for the welfare of global populations though are in part explained by material considerations—particularly risks of continued health threats from a failure to vaccinate globally. Strategic considerations are of more limited importance in shaping public opinion; in particular we see no evidence for free riding on contributions by other states. Finally, drawing on an additional survey experiment, we show that there is scope to use information campaigns highlighting international health externalities to augment public support for global campaigns.
I provide an illustration of a dynamic version of Robert Bates’ conjecture that technologies of coercion can be critical to generate prosperity. The model provides support for the conjecture under specified conditions, generates implications for growth paths, including transitions away from coercive strategies, and has implications for the evolution of inequality.
COVID-19 Vaccine Acceptance and Hesitancy in Low- and Middle-Income Countries
Widespread acceptance of COVID-19 vaccines is crucial for achieving sufficient immunization coverage to end the global pandemic, yet few studies have investigated COVID-19 vaccination attitudes in lower-income countries, where large-scale vaccination is just beginning. We analyze COVID-19 vaccine acceptance across 15 survey samples covering 10 low- and middle-income countries (LMICs) in Asia, Africa and South America, Russia (an upper-middle-income country) and the United States, including a total of 44,260 individuals. We find considerably higher willingness to take a COVID-19 vaccine in our LMIC samples (mean 80.3%; median 78%; range 30.1 percentage points) compared with the United States (mean 64.6%) and Russia (mean 30.4%). Vaccine acceptance in LMICs is primarily explained by an interest in personal protection against COVID-19, while concern about side effects is the most common reason for hesitancy. Health workers are the most trusted sources of guidance about COVID-19 vaccines. Evidence from this sample of LMICs suggests that prioritizing vaccine distribution to the Global South should yield high returns in advancing global immunization coverage. Vaccination campaigns should focus on translating the high levels of stated acceptance into actual uptake. Messages highlighting vaccine efficacy and safety, delivered by healthcare workers, could be effective for addressing any remaining hesitancy in the analyzed LMICs.
Incentives can spur COVID-19 vaccination uptake
Heike Klüver, Felix Hartmann, Macartan Humphreys, Ferdinand Geissler, and 1 more author
Proceedings of the National Academy of Sciences 2021
Recent evidence suggests that vaccination hesitancy is too high in many countries to sustainably contain COVID-19. Using a factorial survey experiment administered to 20,500 online respondents in Germany, we assess the effectiveness of three strategies to increase vaccine uptake, namely, providing freedoms, financial remuneration, and vaccination at local doctors. Our results suggest that all three strategies can increase vaccination uptake on the order of two to three percentage points (PP) overall and five PP among the undecided. The combined effects could be as high as 13 PP for this group. The returns from different strategies vary across age groups, however, with older cohorts more responsive to local access and younger cohorts most responsive to enhanced freedoms for vaccinated citizens.
Falling living standards during the COVID-19 crisis: Quantitative evidence from nine developing countries
Dennis Egger, Edward Miguel, Shana S Warren, Ashish Shenoy, and 7 more authors
Despite numerous journalistic accounts, systematic quantitative evidence on economic conditions during the ongoing COVID-19 pandemic remains scarce for most low- and middle-income countries, partly due to limitations of official economic statistics in environments with large informal sectors and subsistence agriculture. We assemble evidence from over 30,000 respondents in 16 original household surveys from nine countries in Africa (Burkina Faso, Ghana, Kenya, Rwanda, Sierra Leone), Asia (Bangladesh, Nepal, Philippines), and Latin America (Colombia). We document declines in employment and income in all settings beginning March 2020. The share of households experiencing an income drop ranges from 8 to 87% (median, 68%). Household coping strategies and government assistance were insufficient to sustain precrisis living standards, resulting in widespread food insecurity and dire economic conditions even 3 months into the crisis. We discuss promising policy responses and speculate about the risk of persistent adverse effects, especially among children and other vulnerable groups.
Banerjee, Duflo, and Kremer have had an enormous impact on scholarship on the political economy of development. But as RCTs have become more central in this field, political scientists have struggled to draw implications from proliferating micro-level studies for longstanding macro level problems. We describe these challenges and point to recent innovations to help address them.
This study integrates three related field experiments to learn about how information communications technology (ICT) innovations can affect who communicates with politicians. We implemented a nationwide experiment in Uganda following a smaller-scale framed field experiment that suggested that ICTs can lead to significant “flattening”: marginalized populations used short message service (SMS) based communication at relatively higher rates compared to existing political communication channels. We find no evidence for these effects in the national experiment. Instead, participation rates are extremely low, and marginalized populations engage at especially low rates. We examine possible reasons for these differences between the more controlled and the scaled-up experiments. The evidence suggests that even when citizens have issues they want to raise, technological fixes to communication deficits can be easily undercut by structural weaknesses in political systems.
Critics of field experiments lament a turn away from theory and criticize findings for weak external validity. In this chapter, we outline strategies to address these challenges. Highlighting the connection between these twin critiques, we discuss how structural approaches can both help design experiments that maximize the researcher’s ability to learn about theories and enable researchers to judge to what extent the results of one experiment can travel to other settings. We illustrate with a simulated analysis of a bargaining problem to show how theory can help make external claims with respect to both populations and treatments and how combining random assignment and theory can both sharpen learning and alert researchers to over-dependence on theory.
Voter information campaigns and political accountability: Cumulative findings from a preregistered meta-analysis of coordinated trials
Voters may be unable to hold politicians to account if they lack basic information about their representatives’ performance. Civil society groups and international donors therefore advocate using voter information campaigns to improve democratic accountability. Yet, are these campaigns effective? Limited replication, measurement heterogeneity, and publication biases may undermine the reliability of published research. We implemented a new approach to cumulative learning, coordinating the design of seven randomized controlled trials to be fielded in six countries by independent research teams. Uncommon for multisite trials in the social sciences, we jointly preregistered a meta-analysis of results in advance of seeing the data. We find no evidence overall that typical, nonpartisan voter information campaigns shape voter behavior, although exploratory and subgroup analyses suggest conditions under which informational campaigns could be more effective. Such null estimated effects are too seldom published, yet they can be critical for scientific progress and cumulative, policy-relevant learning.
Exporting democratic practices: Evidence from a village governance intervention in Eastern Congo
We study a randomized Community Driven Reconstruction (CDR) intervention that provided two years of exposure to democratic practices in 1250 villages in eastern Congo. To assess its impact, we examine behavior in a village-level unconditional cash transfer project that distributed $1000 to 457 treatment and control villages. The unconditonal cash transfer provides opportunities to assess whetherpublic funds get captured, what governance practices are employed by villagers and village elites and whether prior exposure to the CDR intervention alters these behaviors. We find no evidence for such effects. The results cast doubt on current attempts to export democratic practices to local communities.
Researchers need to select high-quality research designs and communicate those designs clearly to readers. Both tasks are difficult. We provide a framework for formally “declaring” the analytically relevant features of a research design in a demonstrably complete manner, with applications to qualitative, quantitative, and mixed methods research. The approach to design declaration we describe requires defining a model of the world (M), an inquiry (I), a data strategy (D), and an answer strategy (A). Declaration of these features in code provides sufficient information for researchers and readers to use Monte Carlo techniques to diagnose properties such as power, bias, accuracy of qualitative causal inferences, and other “diagnosands.” Ex ante declarations can be used to improve designs and facilitate preregistration, analysis, and reconciliation of intended and actual analyses. Ex post declarations are useful for describing, sharing, reanalyzing, and critiquing existing designs. We provide open-source software, DeclareDesign, to implement the proposed approach.
Citizen attitudes toward traditional and state authorities: substitutes or complements?
Do citizens view state and traditional authorities as substitutes or complements? Past work has been divided on this question. Some scholars point to competition between attitudes toward these entities, suggesting substitution, whereas others highlight positive correlations, suggesting complementarity. Addressing this question, however, is difficult, as it requires assessing the effects of exogenous changes in the latent valuation of one authority on an individual’s support for another. We show that this quantity—a type of elasticity—cannot be inferred from correlations between support for the two forms of authority. We employ a structural model to estimate this elasticity of substitution using data from 816 villages in the Democratic Republic of Congo and plausibly exogenous rainfall and conflict shocks. Despite prima facie evidence for substitution logics, our model’s outcomes are consistent with complementarity; positive changes in citizen valuation of the chief appear to translate into positive changes in support for the government.
Racial discrimination persists despite established antidiscrimination laws. A common government strategy to deter discrimination is to publicize the law and communicate potential penalties for violations. We study this strategy by coupling an audit experiment with a randomized intervention involving nearly 700 landlords in New York City and report the first causal estimates of the effect on rental discrimination against blacks and Hispanics of a targeted government messaging campaign. We uncover discrimination levels higher than prior estimates indicate, especially against Hispanics, who are approximately 6 percentage points less likely to receive callbacks and offers than whites. We find suggestive evidence that government messaging can reduce discrimination against Hispanics but not against blacks. The findings confirm discrimination’s persistence and suggest that government messaging can address it in some settings, but more work is needed to understand the conditions under which such appeals are most effective.
Gender quotas in development programming: Null results from a field experiment in Congo
Peter Windt, Macartan Humphreys, and Raul Sanchez Sierra
We examine whether gender quotas introduced by development agencies empower women. As part of a development program, an international organization created community management committees in 661 villages to oversee village level program expenditures. In a randomly selected half of these villages the organization required the committees to have gender parity. Using data on project choice from all participating villages, data on decision making in a later development project (105 villages), and data on citizen attitudes (200 villages), we find no evidence that gender parity requirements empower women. We discuss potential reasons for the null result, including weakness of these social interventions in terms of the engagement they generate, their time horizon, and the weak delegation of responsibilities.
We examine a public goods game in 83 communities in northern Liberia. Women contributed substantially more to a small-scale development project when playing with other women than in mixed-gender groups, where they contributed at about the same levels as men. We try to explain this composition effect using a structural model, survey responses, and a second manipulation. Results suggest women in the all-women condition put more weight on co-operation regardless of value of public good, fear of discovery, or desire to match others’ behaviour. Game players may have stronger motivation to signal public-spiritedness when primed to consider themselves representatives of the women of the community.
Commentary: Biases in the assessment of long-run effects of deworming
"Jullien and colleagues provide a critique of three working papers on the long-run effects of deworming interventions. Despite being unpublished, these three papers have been prominent in the public debate in support of calls for such interventions over the past few years. What can we really infer from them?"
Poor-quality data about conflict events can hinder humanitarian responses and bias academic research. There is increasing recognition of the role that new information technologies can play in producing more reliable data faster. We piloted a novel data-gathering system in the Democratic Republic of Congo in which villagers in a set of randomly selected communities report on events in real time via short message service. We first describe the data and assess its reliability. We then examine the usefulness of such “crowdseeded” data in two ways. First, we implement a downstream experiment on aid and conflict and find evidence that aid can lead to fewer conflict events. Second, we examine conflict diffusion in Eastern Congo and find evidence that key dynamics operate at very micro levels. Both applications highlight the benefit of collecting conflict data via cell phones in real time.
We develop an approach to multimethod research that generates joint learning from quantitative and qualitative evidence. The framework—Bayesian integration of quantitative and qualitative data (BIQQ)—allows researchers to draw causal inferences from combinations of correlational (cross-case) and process-level (within-case) observations, given prior beliefs about causal effects, assignment propensities, and the informativeness of different kinds of causal-process evidence. In addition to posterior estimates of causal effects, the framework yields updating on the analytical assumptions underlying correlational analysis and process tracing. We illustrate the BIQQ approach with two applications to substantive issues that have received significant quantitative and qualitative treatment in political science: the origins of electoral systems and the causes of civil war. Finally, we demonstrate how the framework can yield guidance on multimethod research design, presenting results on the optimal combinations of qualitative and quantitative data collection under different research conditions.
Social cooperation is critical to a wide variety of political and economic outcomes. For this reason, international donors have embraced interventions designed to strengthen the ability of communities to solve collective-action problems, especially in post-conflict settings. We exploit the random assign- ment of a development program in Liberia to assess the effects of such interventions. Using a matching funds experiment we find evidence that these interventions can alter cooperation capacity. However, we observe effects only in communities in which, by design, both men and women faced the collective action challenge. Focusing on mechanisms, we find evidence that program effects worked through improvements in mobilization capacity that may have enhanced communities’ ability to coordinate to solve mixed gender problems. These gains did not operate in areas where only women took part in the matching funds experiment, possibly because they could rely on traditional institutions unaffected by the external intervention. The combined evidence suggests that the impact of donor interventions designed to enhance cooperation can depend critically on the kinds of social dilemmas that communities face, and the flexibility they have in determining who should solve them.
Promoting an open research culture
Brian A Nosek, George Alter, George C Banks, Denny Borsboom, and 7 more authors
Social scientists are increasingly engaging in experimental research projects of importance for public policy in developing areas. While this research holds the possibility of producing major social benefits, it may also involve manipulating populations, often without consent, sometimes with potentially adverse effects, and often in settings with obvious power differentials between researcher and subject. Such research is currently conducted with few clear ethical guidelines. In this paper I discuss research ethics as currently understood in this field, highlighting the limitations of standard procedures and the need for the construction of appropriate ethics, focusing on the problems of determining responsibility for interventions and assessing appropriate forms of consent.
How does access to information communication technology (ICT) affect who gets heard and what gets communicated to politicians? On the one hand, ICT can lower communication costs for poorer constituents; on the other, technological channels may be used disproportionately more by the already well connected. To assess the flattening effects of ICTs, we presented a representative sample of constituents in Uganda with an opportunity to send a text message to their representatives at one of three randomly assigned prices. Critically, and contrary to concerns that technological innovations benefit the privileged, we find evidence that ICT can lead to significant flattening: a greater share of marginalized populations use this channel compared to existing political communication channels. Price plays a more complex role. Subsidizing the full cost of messaging increases uptake by over 40%. Surprisingly however, subsidy-induced increases in uptake do not yield further flattening since free channels are not used at higher rates by more marginalized constituents.
The elements of political persuasion: Content, charisma and cue
Torun Dewan, Macartan Humphreys, and Daniel Rubenson
Political campaigns employ complex strategies to persuade voters to support them. We analyse the contributions of elements of these strategies using data from a field experiment that randomly assigned canvassers to districts, as well as messaging and endorsement conditions. We find evidence for a strong overall campaign effect and show effects for both message-based and endorsement-based campaigns. However, we find little evidence that canvassers varied according to their persuasive ability or that endorser identity matters. Overall the results suggest a surprisingly muted role for idiosyncratic features of prospective persuaders.
Promoting transparency in social science research
Edward Miguel, Colin Camerer, Katherine Casey, Joshua Cohen, and 7 more authors
In this article, we survey recent progress toward research transparency in the social sciences and make the case for standards and practices that help realign scholarly incentives with scholarly values. We argue that emergent practices in medical trials provide a useful, but incomplete, model for the social sciences. New initiatives in social science seek to create norms that, in some cases, go beyond what is required of medical trials.
Social scientists generally enjoy substantial latitude in selecting measures and models for hypothesis testing. Coupled with publication and related biases, this latitude raises the concern that researchers may intentionally or unintentionally select models that yield positive findings, leading to an unreliable body of published research. To combat this “fishing” problem in medical studies, leading journals now require preregistration of designs that emphasize the prior identification of dependent and independent variables. However, we demonstrate here that even with this level of advanced specification, the scope for fishing is considerable when there is latitude over selection of covariates, subgroups, and other elements of an analysis plan. These concerns could be addressed through the use of a form of comprehensive registration. We experiment with such an approach in the context of an ongoing field experiment for which we drafted a complete “mock report” of findings using fake data on treatment assignment. We describe the advantages and disadvantages of this form of registration and propose that a comprehensive but nonbinding approach be adopted as a first step to combat fishing by social scientists. Likely effects of comprehensive but nonbinding registration are discussed, the principal advantage being communication rather than commitment, in particular that it generates a clear distinction between exploratory analyses and genuine tests.
Gerrymandering produces oddly shaped constituencies that result in electoral outcomes that are unrepresentative of population preferences. This note shows that no shape constraints can prevent gerrymandering and indeed odd shapes may be required to ensure minimal representativeness; this clarifies that the problem of representativeness follows from two party first past the post system, not from the shape of constituencies.
Ethnicity and the Politics of AIDS: A Discussion of Boundaries of Contagion: How Ethnic Politics Have Shaped Government Responses to AIDS
In this review, I argue that Evan Lieberman makes a strong case for the main claim, although the causal argument for the main claim is perhaps not as strong as he suggests. The two explanatory claims give a novel and precise account for why strong ethnic boundaries could have negative effects on AIDS policy. These claims resonate but they do not fully convince; the empirical support for them is narrow relative to the support for the main claim, and the claims seem unable to account for the many alternative strategic possibilities.
Long-standing results demonstrate that, if policy choices are defined in spaces with more than one dimension, majority-rule equilibrium fails to exist for a general class of smooth preference profiles. This article shows that if agents perceive political similarity and difference in ‘city block’ terms, then the dimension-by-dimension median can be a majority-rule equilibrium even in spaces with an arbitrarily large number of dimensions and it provides necessary and sufficient conditions for the existence of such an equilibrium. This is important because city block preferences accord more closely with empirical research on human perception than do many smooth preferences. It implies that, if empirical research findings on human perceptions of similarity and difference extend also to perceptions of political similarity and difference, then the possibility of equilibrium under majority rule re-emerges.
Social scientists have begun to work alongside developing country governments, nongovernmental organizations, and international organizations on experimental projects that address fundamental questions in the political economy of development. We describe the range of projects that have taken place or are currently under-way, identify new and promising frontiers for research, and discuss some challenges that are particular to work in this area. The impact of this research will depend on the extent to which scholars can successfully link studies of experimental interventions to broader questions of social scientific interest.
Can development aid contribute to social cohesion after civil war? Evidence from a field experiment in post-conflict Liberia
We couple a field experiment with behavioral measures in Liberia to try to work out whether community driven development interventions affect the ways that communities can work together. We find no evidence for adverse effects and some surprisingly strong evidence that exposure to development aid can strengthen the ability of communities to work together.
New work attempts to address these shortcomings by modeling coalition formation as an explicitly noncooperative process. This new research reintroduces the problem of coalitional instability characteristic of cooperative approaches, but in a dynamic setting. Although in some settings, classic solutions are recovered, in others this new work shows that outcomes are highly sensitive, not only to bargaining protocols, but also to the forms of commitment that can be externally enforced. This point of variation is largely ignored in empirical research on coalition formation. I close by describing new agendas in coalitional analysis that are being opened up by this new approach.
When a single group uses majority rule to select a set of policies from an n-dimensional compact and convex set, a core generally exists if and only if n=1. Finding analogous conditions for core existence when an n-dimensional action requires agreement from m groups has been an open problem. This paper provides a solution to this problem by establishing sufficient conditions for core existence and characterizing the location and dimensionality of the core for settings in which voters have Euclidean preferences.
A range of seemingly rival theories attempt to explain why some individuals take extraordinary risks by choosing to participate in armed conflict. To date, however, competing accounts have typically not been grounded in systematic, empirical studies of the determinants of participation. In this article, we begin to fill this gap through an examination of the determinants of participation in insurgent and counterinsurgent factions in Sierra Leone’s civil war. We find some support for all of the competing theories, suggesting that the rivalry between them is artificial and that theoretical work has insufficiently explored the interaction of various recruitment strategies. At the same time, the empirical results challenge standard interpretations of grievance-based accounts of participation, as poverty, a lack of access to education, and political alienation predict participation in both rebellion and counterrebellion. Factors that are traditionally seen as indicators of grievance or frustration may instead proxy a for more general susceptibility to engage in violent action or a greater vulnerability to political manipulation by elites.
A large and growing literature links high levels of ethnic diversity to low levels of public goods provision. Yet although the empirical connection between ethnic heterogeneity and the underprovision of public goods is widely accepted, there is little consensus on the specific mechanisms through which this relationship operates. We identify three families of mechanisms that link diversity to public goods provision—what we term “preferences,” “technology,” and “strategy selection” mechanisms—and run a series of experimental games that permit us to compare the explanatory power of distinct mechanisms within each of these three families. Results from games conducted with a random sample of 300 subjects from a slum neighborhood of Kampala, Uganda, suggest that successful public goods provision in homogenous ethnic communities can be attributed to a strategy selection mechanism: in similar settings, co-ethnics play cooperative equilibria, whereas non-co-ethnics do not. In addition, we find evidence for a technology mechanism: co-ethnics are more closely linked on social networks and thus plausibly better able to support cooperation through the threat of social sanction. We find no evidence for prominent preference mechanisms that emphasize the commonality of tastes within ethnic groups or a greater degree of altruism toward co-ethnics, and only weak evidence for technology mechanisms that focus on the impact of shared ethnicity on the productivity of teams.
Lots of resources are put into assisting ex-combatants return to civilian life. But we don’t understand the reintegration process well and whether interventions to support it are effective. We find that a history of abuse is a good predictor of reintegration difficulties but we find no evidence of the effectiveness of UN programs, although we emphasize that no evidence of an effect is not the same as evidence of no effect.
I examine the conjecture that bargainers are much more effective when their deals are subject to ratification by third parties with different preferences to their own. By examining a general setting in which ratifiers are fully strategic I find conditions under which this conjecture holds.
We use a field experiment to work out how participatory processes really are. We examine an ambitious exercise in deliberative democracy in Sao Tome e Principe and find that outcomes of group deliberations are strongly determined by who happens to be facilitating the discussions. Participatory processes may be much more open to manipulation than we tend to think.
We seek to understand why some fighting factions are so much more abusive to civilian populations than others. There are many possible reasons for this; in the Sierra Leone case variation in the discipline of subfactional units appears best able to account for behavior with civilians. Within both the rebel and the militia groups abuses were significantly more limited in the more disciplined units.
We examine the effects of democratic institutions on policy choices; we find that more competitive systems are associated with less corruption but not with a greater propensity to adopt “Washington Consensus” policies
The interpretation of the resource-conflict link that has become most publicized—the rebel greed hypothesis—depends on just one of many plausible mechanisms that could underlie a relationship between resource dependence and violence. The author catalogues a large range of rival possible mechanisms, highlights a set of techniques that may be used to identify these mechanisms, and begins to employ these techniques to distinguish between rival accounts of the resource-conflict linkages. The author uses finer natural resource data than has been used in the past, gathering and presenting new data on oil and diamonds production and on oil stocks. The author finds evidence that (1) conflict onset is more responsive to the impacts of past natural resource production than to the potential for future production, supporting a weak states mechanism rather than a rebel greed mechanism; (2) the impact of natural resources on conflict cannot easily be attributed entirely to the weak states mechanism, and in particular, the impact of natural resources is independent of state strength; (3) the link between primary commodities and conflict is driven in part by agricultural dependence rather than by natural resources more narrowly defined, a finding consistent with a “sparse networks” mechanism; (4) natural resources are associated with shorter wars, and natural resource wars are more likely to end with military victory for one side than other wars. This is consistent with evidence that external actors have incentives to work to bring wars to a close when natural resource supplies are threatened. The author finds no evidence that resources are associated with particular difficulties in negotiating ends to conflicts, contrary to arguments that loot-seeking rebels aim to prolong wars.
Connaître les causes économiques des conflits et les structures des économies de guerre aide à comprendre et à promouvoir le développement économique. Cet article présente les travaux quantitatifs récents dans le domaine des guerres civiles, à partir des apports de recherches plus qualitatives. L’auteur étudie le rôle de la richesse, de l’inégalité, des ressources naturelles et des politiques économiques sur les conflits, leur coût, les activités des rebelles, des entreprises et des communautés internationales. Il insiste enfin sur les domaines restant à explorer.