journal articles

Cooperation, Conflict, and the Costs of Anarchy.  International Organization (forthcoming 2018).  pdf draft 

Civil War and the Current International System.  Daedalus 146 (Fall 2017). pdf draft 

How Does Development Affect Collective Action Capacity?  Results from a Field Experiment in Post-Conflict Liberia (co-authored with Macartan Humphreys and Jeremy Weinstein). American Political Science Review 109, 3 (August 2015), 450-469.  

Self-Enforcing DemocracyQuarterly Journal of Economics 126 (November 2011), 1661-1708.  

Sons of the Soil, Migrants, and Civil War (co-authored with David Laitin). World Development 39, 2 (2011), 199-211.   next-to-last word version

Can Development Aid Contribute to Social Cohesion after Civil War? Evidence from a Field Experiment in Post-Conflict Liberia. (co-authored with Macartan Humphreys and Jeremy M. Weinstein). American Economic Review: Papers and Proceedings 2009, 99:2, 287-291.

Iraq’s Civil WarForeign Affairs 86, 2 (March/April 2007), 2-16.

Ethnic Minority Rule and Civil War Onset (co-authored with Kimuli Kasara and David Laitin). American Political Science Review 101, 1 (February 2007), 187-193.

Primary Commodity Exports and Civil WarJournal of Conflict Resolution 49, 4 (August 2005), 483-507. 

Separatist Wars, Partition, and World OrderSecurity Studies 13, 4 (Summer 2004), 394-415. 

Neotrusteeship and the Problem of Weak States. (co-authored with David Laitin). International Security 28, 4 (Spring 2004), 5-43.

Why Do Some Civil Wars Last So Much Longer Than Others? Journal of Peace Research 41, 3 (May 2004), 275-302. 

Ethnic and Cultural Diversity by Country Journal of Economic Growth 8, 2 (June 2003), 195-222. 

Ethnicity, Insurgency, and Civil War (co-authored with David Laitin). American Political Science Review 97, 1 (February 2003), 75-90.  

Selection Effects and DeterrenceInternational Interactions 28, 1 (January-March 2002), 5-29. 

Violence and the Social Construction of Ethnic Identity (co-authored with David Laitin.) International Organization 54, 4 (Autumn 2000), 845-877.

Bargaining, Enforcement, and International CooperationInternational Organization 52, 2 (Spring 1998), 269-306. 

Signaling Foreign Policy Interests: Tying Hands versus Sinking Costs. Journal of Conflict Resolution 41, 1 (February 1997), 68-90. 

Explaining Interethnic Cooperation. (Co-authored with David Laitin.) American Political Science Review 90, 4 (December 1996), 715-35. 

Rationalist Explanations for WarInternational Organization 49 (Summer 1995), 379-414. 

Domestic Political Audiences and the Escalation of International Disputes. American Political Science Review 88 (September 1994), 577-92. 

Signaling versus the Balance of Power and Interests An Empirical Test of a Crisis Bargaining Model. Journal of Conflict Resolution 38 (June 1994, Special Issue), 236-69. 

Counterfactuals and Hypothesis Testing in Political Science. World Politics 43 (January 1991), 169-95. 

International Financial Institutions and Economic Policy Reform in Sub-Saharan Africa. Journal of Modern African Studies 26 (March 1988), 113-137.


I consider a model in which two states choose how much to arm and whether to attack in successive periods. Arms are useful not only for deterrence or taking territory, but also because they influence the resolution of a set of disputed issues. It is shown that states can cooperate on the issues by limiting military competition, but only as far as a “war constraint” allows. Factors determining the tightness of the war constraint imply hypotheses about the international determinants of military effort and thus the costs of anarchy. The strategic logic differs from standard security dilemma arguments, in which the costs of anarchy are associated with conflict between status quo states that are uncertain about others’ territorial revisionism. Here, inefficiency arises because arming to deter lowers a state’s value for living with the status quo, which creates a security externality and a feedback loop. The model both synthesizes and revises a diverse range of theoretical arguments about the determinants of interstate cooperation and conflict.

This essay sketches an explanation for the global spread of civil war up to the early 1990s and the partial recession since then, arguing that some of the decline is likely due to policy responses by major powers working principally through the United Nations. Unfortunately, the spread of civil war and state collapse to the Middle East and North Africa region in the last 15 years has posed one set of problems that the current policy repertoire cannot address well — for several reasons conflicts in this region are resistant to “treatment” by international peacekeeping operations — and highlighted a second, deeper problem whose effects are gradually worsening and for which there does not appear to be any good solution within the constraints of the present UN system. This is that for many civil-war torn or post-conflict countries, third parties do not know how to help locals build a self-governing, self-financing state within U.N. recognized borders or, in some cases, any borders.

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 assignment 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.

If democracy is to have the good effects said to justify it, it must be self-enforcing in that incumbents choose to hold regular, competitive elections and comply with the results. I consider models of electoral accountability that allow rulers a choice of whether to hold elections and citizens whether to rebel. When individuals observe diverse signals of government performance, coordination to pose a credible threat of protest if the ruler “shirks” is problematic. The convention of an electoral calendar and known rules can provide a public signal for coordinating rebellion if elections are suspended or blatantly rigged, while the elections themselves aggregate private observations of performance. Two threats to this solution to political moral hazard are considered. First, a ruling faction that controls the army may prefer to fight after losing an election, and ex post transfers may not be credible. A party system in which today’s losers may win in the future can restore self-enforcing democracy, though at the cost of weaker electoral control.  Second, subtle electoral fraud can undermine the threat of coordinated opposition that maintains elections. I show that when there are organizations in society that can observe and announce a signal of the extent of popular discontent, the incumbent may prefer to commit to fair elections over an “accountable autocratic” equilibrium in which public goods are provided but costly rebellions periodically occur. JEL Codes: D02, D72, H11.

 In nearly a third of ethnic civil wars since 1945, the conflict develops between members of a regional ethnic group that considers itself to be the indigenous “sons of the soil” and recent migrants from other parts of the country. The migrants are typically members of the dominant ethnic group who migrate in search of land or government jobs, often supported by the state with economic incentives and development schemes. This paper elaborates on the concept of a sons-of-the-soil conflict; presents descriptive statistics and empirical patterns; identifies a typical escalation sequence; illustrates the several steps with an account of the Tamil-Sinhalese conflict along with other cases; discusses the obstacles to negotiated settlements; and concludes with a suggestion on the role of grievances in explaining civil war onsets.
 Collier and Hoeffler reported that countries with a higher percentage of national income from primary commodity exports have been more prone to civil war, an interesting finding that has received much attention from policy makers and the media. The author shows that this result is quite fragile, even using Collier and Hoeffler’s data. Minor changes in the sample framing and the recovery of missing data undermine it. To the extent that there is an association, it is likely because oil is a major component of primary commodity exports and substantial oil production does associate with civilwar risk. The author argues that oil predicts civil war risk not because it provides an easy source of rebel start-up finance but probably because oil producers have relatively lowstate capabilities given their level of per capita income and because oil makes state or regional control a tempting “prize.” An analysis of data on government observance of contracts and investor-perceived expropriation risk is consistent with this hypothesis.
Should ethnonationalist wars be resolved by formally partitioning states? The answer can’t be decided case by case, because two incentive problems imply that ad hoc partitions have effects that extend across cases. First, if the implicit criterion for major power intervention in support of partition is some level of violence, this encourages violent movements seeking to mobilize cultural difference in order to claim statehood. The Wilsonian diagnosis is wrong.  Perpetual civil peace cannot be had by properly sorting “true” nations into states, because nations are not born but made, partially in response to international incentives and major power policies. Second, an international order in which major powers go around carving up lesser powers on an ad hoc basis would make all states significantly less secure. Ad hoc use of partition to solve civil wars would undermine a relatively stable implicit bargain among the major powers in place since the 1950s – “If you don’t seek to change interstate borders by force, neither will we.” I argue that this norm has been valuable, functioning in some respects like an arms control agreement. It would be irresponsible to undermine it without a thought to what might replace it, as the advocates of ad hoc partition are effectively urging. If the major powers want to start redesigning “sovereign” states, they need a political and legal framework that mitigates these two incentive effects. The best feasible solutions may be: (1) strengthening and making more precise international legal standards on human (and perhaps group) rights; (2) threatening to sanction states that do not observe these standards in regard to minorities, possibly including some forms of support for agents of the oppressed group; (3) holding to the norm of partition only by mutual consent, but providing carrots and sticks when the state in question refuses to abide by minimal standards of nondiscrimination.
 Five factors are shown to be strongly related to civil war duration. Civil wars emerging from coups or revolutions tend to be short. Civil wars in Eastern Europe and the former Soviet Union have also tended to be relatively brief, as have anti-colonial wars. By contrast, ‘sons of the soil’ wars that typically involve land conflict between a peripheral ethnic minority and state-supported migrants of a dominant ethnic group are on average quite long-lived. So are conflicts in which a rebel group derives major funding from contraband such as opium, diamonds, or coca. The article seeks to explain these regularities, developing a game model focused on the puzzle of what prevents negotiated settlements to long-running, destructive civil wars for which conflicting military expectations are an implausible explanation. In the model, regional autonomy deals may be unreachable when fluctuations in state strength undermine the government’s ability to commit. The commitment problem binds harder when the center has an enduring political or economic interest in expansion into the periphery, as in ‘sons of the soil’ wars, and when either government or rebels are able to earn some income during a conflict despite the costs of fighting, as in the case of contraband funding.
 For their empirical evaluation, several active research programs in economics and political science require data on ethnic groups across countries. “Ethnic group,” however, is a slippery concept. After addressing conceptual and practical obstacles, I present a list of 822 ethnic groups in 160 countries that made up at least 1 percent of the country population in the early 1990s. I compare a measure of ethnic fractionalization based on this list with the most commonly used measure. I also construct an index of cultural fractionalization that uses the structural distance between languages as a proxy for the cultural distance between groups in a country.
An influential conventional wisdom holds that civil wars proliferated rapidly with the end of the Cold War and that the root cause of many or most of these has been ethnic nationalism. We show that the current prevalence of internal war is mainly the result of a steady accumulation of protracted conflicts since the 50s and 60s rather than a sudden change associated with a new, post-Cold War international system. We also find that after controlling for per capita incomes and growth rates, more ethnically or religiously diverse countries have been no more likely to experience signifi cant civil war in this period. We argue for understanding civil war in this period in terms of insurgency or rural guerrilla warfare, a particular form of military practice that can be harnessed to diverse political agendas, including but not limited to ethnic nationalism. The factors that explain which countries have been at risk for civil war are not their ethnic or religious characteristics but rather the conditions that favor insurgency. These include poverty and slow growth, which favor rebel recruitment and mark nancially and bureaucratically weak states, rough terrain, and large populations.
 The empirical question of how often deterrent threats issued during international disputes succeed has been hotly debated for years, with some researchers arguing that virtually no robust cases of success can be identified. I argue that what appears to be an empirical and methodological debate actually arises from the inadequacy of classical rational deterrence theory, which fails to comprehend the implications of states’ strategic self-selection into international disputes. Rational self-selection is shown to imply that in a sample of crises, deterrent threats issued after an initial challenge will tend to fail in precisely those cases where they are relatively most credible signals of an intent to resist with force. The product of a selection effect, this paradoxical implication allows a resolution of the debate on the efficacy of deterrence in crises. And because selection effects can arise whenever a historical “case” is the product of choices by actors who also influence the outcome in question, this example from the study of deterrence has broad relevance for empirical research.
We examine the theoretical implications of the observation that ethnic identities are socially constructed for explaining ethnic violence, distinguishing between two classes of mechanisms. If individuals are viewed as the agents who construct identities, then constructivist explanations for ethnic violence tend to merge with analyses that stress strategic action by both elites and mass publics. In contrast, if discursive formations are the agents that construct ethnic identities, then constructivist explanations tend to merge with accounts that stress internal logics of specific cultures. Using the books under review as a “sample,” we find considerable evidence linking strategic aspects of ethnic identity construction to violence and more limited evidence implicating discursive systems. The most common narrative in these texts has largescale ethnic violence provoked by elites, often motivated by intra-ethnic conflicts. Followers follow, despite the costs, out of increased fear of thugs and armies “let go” by elites (both the other side’s and their “own”) and often in pursuit of local grievances that may have little ethnic component. Several other mechanisms are also discussed, including the role of discursive systems in conditioning publics for violence and the role of violent efforts to enforce “everyday primordialism” by policing supposedly primordial ethnic boundaries.
 Neoliberals and their neorealist critics have debated the relative importance of two main obstacles to international cooperation—problems of cheating and enforcement and problems of relative gains. By contrast, I argue that problems of international cooperation have a common strategic structure in which a third, distinct obstacle plays a crucial role. Almost regardless of the issue area, states must first resolve the bargaining problem of agreeing on terms before they can implement and begin to enforce an agreement. Furthermore, the bargaining and enforcement problems interact. Using a game model, I show that if states must bargain to determine the deal to be enforced, the “shadow of the future” cuts two ways. A high expectation of continued interactions may make enforcing the agreement easier, but it can also give states an incentive to bargain harder, delaying agreement in hopes of getting a better deal. Empirical evidence from trade and arms control negotiations suggests that this mechanism may help to explain the costly standoffs that are often observed in international politics and are problematic for received neoliberal theories.
 The author distinguishes between two types of costly signals that state leaders might employ in trying to credibly communicate their foreign policy interests to other states, whether in the realm of grand strategy or crisis diplomacy. Leaders might either (a) tie hands by creating audience costs that they will suffer ex post if they do not follow through on their threat or commitment (i.e., costs arising from the actions of domestic political audiences) or (b) sink costs by taking actions such as mobilizing troops that are financially costly ex ante. Analysis of a game model depicting the essentials of each case yields two principal results. First, in the games’ equilibria, leaders never bluff with either type of signal; they do not incur or create costs and then fail to respond if challenged. Second, leaders do better on average by tying hands, despite the fact that the ability to do so creates a greater ex ante risk of war than does the use of sunk-cost signals. These results and the logic behind them may help explain some empirical features of international signaling, such as many crises’ appearance as competitions in creating domestic political audience costs. They also generate empirical puzzles, such as why the seemingly plausible logic of inference that undermines bluffing in the model does not operate in all empirical cases.
Though both journalists and the academic literature on ethnic conflict give the opposite impression, a peaceful and even cooperative relations between ethnic groups are far more common than is large-scale violence. We seek to explain this norm of interethnic peace and how it occasionally breaks down, arguing that formal and informal institutions usually work to contain or “cauterize” disputes between individual members of different groups. Using a social matching game model, we show that local-level interethnic cooperation can be supported in essentially two ways. In spiral equilibria, disputes between individuals are correctly expected to spiral rapidly beyond the two parties, and fear of this induces cooperation “on the equilibrium path. ” In in-group policing equilibria, individuals ignore transgressions by members of the other group, correctly expecting that the culprits will be identified and sanctioned by their own ethnic brethren. A range of examples suggests that both equilibria occur empirically and have properties expected from the theoretical analysis.
 Realist and other scholars commonly hold that rationally led states can and sometimes do fight when no peaceful bargains exist that both would prefer to war. Against this view, I show that under very broad conditions there will exist negotiated settlements that genuinely rational states would mutually prefer to a risky and costly fight. Popular rationalist and realist explanations for war fail either to address or to explain adequately what would prevent leaders from locating a less costly bargain. Essentially just two mechanisms can resolve this puzzle on strictly rationalist terms. The first turns on the fact that states have both private information about capabilities and resolve and the incentive to misrepresent it. The second turns on the fact that in specific strategic contexts states may be unable credibly to commit to uphold a mutually preferable bargain. Historical examples suggest that both mechanisms are empirically plausible.
International crises are modeled as a political “war of attrition” in which state leaders choose at each moment whether to attack, back down, or escalate. A leader who backs down suffers 1 audience costs that increase as the public confrontation proceeds. Equilibrium analysis shows how audience costs enable leaders to learn an adversary’s true preferences concerning settlement versus war and thus whether and when attack is rational. The model also generates strong comparative statics results, mainly on the question of which side is most likely to back down. Publicly observable measures of relative military capabilities and relative interests prove to have no direct effect once a crisis begins. Instead, relative audience costs matter: the side with a stronger domestic audience (e.g., a democracy) is always less likely to back down than the side less able to generate audience costs (a non-democracy). More broadly, the analysis suggests that democracies should be able to signal their intentions to other states more credibly and clearly than authoritarian states can, perhaps ameliorating the security dilemma between democratic states.
Conventional wisdom holds that in international disputes, a state’s military threats are more likely to work the more the state is favored by the balance of power or the balance of interests. Analysis of a game-theoretic model of crisis signaling substantially refines and revises this claim. Due to selection effects arising from strategic behavior, measures of the relative strength of a defender’s interests that are available before a crisis begins (ex ante) should be related to the failure of the defender’s threats during the crisis. Ex ante measures of the defender’s relative military strength should correlate with the success of the defender’s crisis threats, but due to strategic dynamics that are not grasped by the standard arguments. A reanalysis of Huth and Russett’s data on immediate deterrent threats lends support for these and other hypotheses drawn from the game-theoretic treatment.
 Scholars in comparative politics and international relations routinely evaluate causal hypotheses by referring to counterfactual cases where a hypothesized causal factor is supposed to have been absent. The methodological status and the viability of this very common procedure are unclear and are worth examining. How does the strategy of counterfactual argument relate, if at all, to methods of hypothesis testing based on the comparison of actual cases, such as regression analysis or Mill’s Method of Difference? Are counterfactual thought experiments a viable means of assessing hypotheses about national and international outcomes, or are they methodologically invalid in principle? The paper addresses the first question in some detail and begins discussion of the second. Examples from work on the causes of World War I, the nonoccurrence of World War III, social revolutions, the breakdown of democratic regimes in Latin America, and the origins of fascism and corporatism in Europe illustrate the use, problems and potential of counterfactual argument in small-N-oriented political science research.