Territoriality, Neighborhood Effects, and the Causes of Civil War*

Idean Salehyan idean@ucsd.edu

Department of Political Science

University of California, San Diego

Abstract: Political opportunity theories of civil violence argue that civil wars are more likely to occur when the state is relatively weak. However, this perspective has ignored political conditions in neighboring states that make conflict more likely. This paper argues that rebel groups often use the territory of neighboring states from which to attack the government. Because of territorial limits on the state’s power, the government is limited in its ability to repress challengers when they are located across a national boundary. Thus, refugee populations and rebels among them in neighboring states are expected to increase the likelihood of conflict. Furthermore, violence will be more common when neighboring states are too weak to control transnational rebel groups and/or when hostile neighboring states encourage rebel groups to take sanctuary there. The theory is supported by a preliminary statistical analysis of civil conflicts in the post-WWII era.

Prepared for the European Consortium for Political Research Joint Sessions of Workshops

Uppsala, Sweden April 13-18, 2004

* Please do not cite without permission of the author. This paper is based on a dissertation proposal and is in its preliminary stages. Comments and suggestions for improvement are greatly appreciated.

Salehyan

Territoriality, Neighborhood Effects, and the Causes of Civil War

Nearly all nascent rebel organizations start off at significant military disadvantage

relative to the state. While the state’s monopoly on the use of force is rarely complete, it is the

preponderant military power within a given territory as it specializes in defense against foreign

enemies as well as maintaining internal order. Groups contemplating rebellion—particularly in

the early phases of a conflict—do not have the troops, resources, and organization to match those

of the government and efforts to mobilize these capabilities invite repression. Overcoming the

state is, therefore, a monumental task. As such, civil wars present an important theoretical

challenge for social scientists: given the large power imbalance between the “Leviathan” and

rebel organizations, why do civil wars occur at all? Why do rebels, who start off relatively weak,

ever attempt to challenge the government?1

The case of Liberia highlights this puzzle. On December 24 of 1989, Charles Taylor and

his rebel organization, the National Patriotic Front of Liberia, launched an insurgency against the

government of Samuel Doe. Patrick Brogan (1998) reports that Taylor’s forces consisted of

roughly 40 men; clearly, this group was vastly outnumbered by Doe’s superior military and

police forces. The NPFL launched its initial strikes from neighboring Cote d’Ivoire, and

concentrated its early efforts on targets in Nimba County which is located along the

Liberian/Ivoirian border. Soon, backing for Taylor materialized as members of the Gio and

Mano ethnic groups, who felt alienated by Doe’s support of his Krahn co-ethnics, joined the

rebellion. After several months of fighting and thousands of deaths, Doe was deposed and later

1 Throughout this paper, I use the terms “rebellion,” “insurgency,” “civil war,” and “armed opposition” interchangeably.

2

Salehyan

executed. How did the tiny NPFL rationally choose to challenge Doe’s government? Why was

the state, which had thousands of troops and armaments, unable to stop a few dozen rebels from

sparking a bloody civil war which would eventually lead to the regime’s collapse?

In the early stages of rebellion—as the case of Liberia demonstrates—the odds of success

seem stacked against potential insurgents. Any steps taken to mobilize an armed political

opposition group are likely to be met with extreme force, and so getting off of the ground is quite

difficult. Moreover, there should be little uncertainty about relative capabilities—which has

been identified as a major cause of international war (Fearon 1995)—as the state has a clear

upper hand in comparison with nascent rebel organizations. Because of their limited capabilities,

rebel organizations have little bargaining power vis-à-vis the government. Given these bleak

prospects, why would rational actors ever mount an armed challenge to the state?

To presage the argument developed below, in line with political opportunity theories of

collective violence, I contend that rebellion is likely to occur when the ability of the state to

impose costs on rebels is low. In particular, the ability to use a neighboring state’s territory

allows rebels to escape repression efforts and thus greatly decreases the cost of rebellion. While

nearly all previous studies have focused on country-level conditions that lead to violence, I argue

that political opportunities to mobilize an insurgency outside of the state may be just as

important as within-country factors, if not more so. As such, NPFL was able to get off of the

ground by strategically positioning itself in Cote d’Ivoire where the Liberian government was

unable to prevent mobilization efforts. Similarly, the PLO used bases in Jordan and Lebanon to

attack Israel, Rwandan Tutsi rebels organized in Uganda, and Burmese rebels have launched

attacks from neighboring Thailand. Thus, if rebel groups can use neighboring territories as a

base of operations, thereby escaping the sovereign jurisdiction of the state, civil wars are more

3

Salehyan

likely to occur. These conditions will present themselves when neighboring countries are weak

and unable to prevent rebel groups from locating on their territory, or when they are hostile to the

target government and thus encourage the insurgents.

However, access to the territory of neighboring countries is simply a permissive

condition that affords rebel groups the ability to fight, but it still does not fully explain why

parties are willing to undertake a costly conflict when a bargained solution would be more

efficient (Fearon 1995). Extraterritorial bases simply alter the cost/benefit calculation of

combatants and should be reflected in the underlying bargain. I argue that conflicts continue

under these conditions because of a credible commitment problem. Rebel groups cannot

credibly commit to cease fighting as long as they have the continued outside option of

establishing bases in neighboring countries. Therefore, the cooperation of the neighboring

country is needed to halt the violence.

This paper is organized as follows. The next section will review the current literature on

civil conflict. The third section presents a new theory, based within the political opportunity

framework, which highlights the importance of neighboring territory in mobilizing and

maintaining an insurgency. I also expand upon the political opportunity literature by examining

how permissive conditions leading to conflict are reflected in the underlying political bargain.

The fourth section presents a preliminary statistical analysis based on the theory developed.

The Literature: Motive and Opportunity

Studies of collective violence against the state have either focused on rebel motives or the

opportunity for rebellion.2 The motive perspective examines the rewards that groups hope to

gain through fighting. Ted Gurr, in his classic book Why Men Rebel (1970) argues that relative

4

Salehyan

deprivation—the disadvantages groups face relative to one another and/or unachieved

aspirations—leads to frustration and aggression, which in turn provides a motive for aggrieved

groups to rebel. Similarly, Muller and Seligson (1987) argue that income inequality generates

discontent and provides a motive to react violently against the state. According to these

“grievance” theories, rebels are primarily concerned with changing policies and practices that

disadvantage their group; collective violence is about redressing real or perceived grievances.

For instance, grievance theories would argue, the Zapatista uprising in southern Mexico was in

response to discrimination against indigenous peoples and neo-liberal economic reforms that

harmed group interests. The Kurdish rebellion against Turkey, to cite another example, is a

direct result of poor economic conditions in Kurdistan and state policies which deny Kurds

cultural rights.

Another more recent line of thought argues that “greed” rather than grievance is a

significant motive for several insurgencies. The desire for profit provides a raison d’être for

some rebel organizations. Collier and Hoeffler (2001) argue that many rebels are not so much

concerned with righting wrongs but with enriching themselves through plunder. This

perspective focuses on the selective incentives, or side benefits unrelated to any stated aims, that

motivate groups to fight. The capture and sale of easily obtainable natural resources such as

diamonds, timber, and narcotics provide an economic rationale for mobilizing a rebel army as the

sale of these commodities is more lucrative than alternative source of income for many rebels.

As such, in Colombia it is argued, rebel organizations are not so much concerned with changing

state policies but with enriching themselves through the sale of narcotics; similarly, “blood

diamonds” have fueled several armed conflicts in Africa.

5

Salehyan

Both the “greed” and “grievance” perspectives highlight important motivations for

rebellion, but explaining motive is not sufficient for explaining insurgency. The grievance

tradition in particular has lost favor among political scientists. Foremost among the critiques is

that grievances are ubiquitous; of all of the potentially aggrieved groups only a small fraction

actually rebel, therefore grievances alone cannot explain insurgent violence (Lichbach 1995;

Tilly 1978) Arguably, all countries contain some group that is disadvantaged relative to others,

but very few experience rebellion. Ironically, in an empirical study, Gurr and Moore (1997)

find little relationship between grievances and rebellion, although they show that grievance may

heighten protest activity.

This same critique can be made of the “greed” perspective, however. Resources for

plunder are frequently available; nearly all countries have some resource that can be looted.

Even if a country is not richly endowed with natural resources, rebel organizations can enrich

themselves through extortion, hostage taking (e.g. Colombia and the Philippines), and other

criminal activities. In other words, grievances and resources for plunder are quite common and

cannot alone explain conflict.

Because motive for rebellion is widespread, most scholars of civil conflict have looked at

opportunity rather than motive in explaining civil conflict. Because insurgency invites

repression, and is thus costly, it is more likely to occur if rebels believe that their probability for

success is high and that the costs of insurgency are low (Lichbach 1995; Tilly 1978). Therefore,

civil wars are more likely when the “Leviathan” is relatively weak and incapable of maintaining

order. Several distinct though complimentary theories about the political opportunity structure

and the likelihood of violence have been proposed. Barry Posen (1993) argues that when the

central state collapses altogether, as happened most vividly in the early 1990’s in the Balkans,

6

Salehyan

groups are provided the opportunity to fight and may be caught in a security dilemma situation.

Internal anarchy after the dissolution of the state leads to conditions conducive to violence that

are similar to the anarchic international environment. However, this cannot explain most

instances of civil conflict as the complete collapse of the state is a rare phenomenon and there are

several instances of rebellion that occur even within a functioning state.

Another argument examines the relationship between democracy, repression, and civil

war. Muller and Weede (1990) and Hegre et al (2001) among others, argue and empirically

demonstrate that there is an inverted-U relationship between autocracy/democracy and civil war.

In the most democratic regimes, violence is less likely because groups can resolve their disputes

through well-established legal and political channels and forgo a costly rebellion. In the most

autocratic and repressive regimes, violence is also less likely because the central state can

successfully thwart challengers through coercion. Civil wars are therefore most likely to occur

in “weak authoritarian” regimes (or anocracies), where democracy is not firmly entrenched and

the capacity of the state to repress challengers is not great. Additionally, Hegre et. al. (2001)

find that during periods of regime transition or instability, in which the state has yet to fully

consolidate power (i.e. it is weak), insurgency is more likely to occur.

Fearon and Laitin (2003) point to several additional variables that diminish the state’s

repressive capabilities and increase the likelihood of civil war. Rough terrain, such as a

mountainous landscape, inhibits the states’ ability to pursue rebels into remote areas and provide

insurgents the opportunity to fight. Income per capita, they further argue, is a good proxy for the

state’s administrative, police, and military capabilities and for infrastructure such as roads and

railways which enable the state to access remote areas in pursuit of rebels. Poor states are less

capable of maintaining order. In Fearon and Laitin’s study, newly independent states are also

7

Salehyan

found to be more likely to experience violence as the central state has yet to fully develop its

capabilities.

Emphasizing political opportunities provides a useful corrective to studies which focus

exclusively on rebel motives. While both motive and opportunity are necessary conditions for

insurgency, there are hundreds (or even thousands) of groups that have adequate motive for

rebellion, whether that motivation be greed or grievance-driven. For practical purposes, because

of the ubiquity of motive, it may be held constant by analysts; focusing on political opportunities

allows for systematic cross-national variation in the explanatory variable. In the next section, I

argue that scholars in the opportunity tradition have rather myopically looked at country-level

indicators to account for political violence, when in fact international factors may explain much

of the action in civil conflict. In particular, I argue that neighboring countries may provide rebel

organizations with the opportunity to mobilize and engage the state.

Territory, Population, and Violence

Most studies of civil conflict have looked at internal country conditions that make violence more

or less likely. However, there is good reason to believe that factors beyond the state and the

regional context in which a state is positioned may be just as important in fostering conflict

and/or promoting peace (Brown 1996; Gleditsch 2002; Lake 1998; Midlarsky 1992). States are

not isolated units, and conditions in one state are likely to affect those nearby—a point that most

of the civil war literature overlooks. The political opportunity literature suffers from at least

three additional shortcomings. First, even a weak state is normally much stronger than most

insurgent groups, particularly when these groups are still in their formative period—there

remains a large power imbalance. Liberia was by no means a strong state in 1989, but it was still

8

Salehyan

vastly stronger than its challenger, the NPFL. Secondly, on empirical grounds, there are several

instances of civil war in which the target government is not particularly weak. India, the UK

(Northern Ireland), and Turkey, to name a few examples, are quite competent states which have

experienced a large degree of internal turmoil.

Lastly, political opportunity theories suggest that conflict is more likely to occur when

state strength is diminished, but this overlooks the key theoretical insight of bargaining theory.

If relative capabilities are known—and political opportunity theories are primarily about

diminished capabilities of the state—groups should in principle be able to reach a bargained

solution to their difference and forgo costly violence. Therefore, bargaining theories of conflict

can be used to complement the political opportunity framework. I will return to this point in

more detail below.

My principal argument is that conditions in neighboring territories are a key determinant

of the opportunity for rebellion, and hence, the probability of civil conflict. Scholars have

devoted much attention to the norms of state sovereignty and territoriality in international

politics (Jackson 1987; Kratochwil 1986; Krasner 1995-1996; Ruggie 1993; Zacher 2001), and

these factors, I argue, play an important role in rebellion. While the norm of state sovereignty

protects states from outside interference in its internal affairs3, territoriality delimits the

geographical scope of the state’s jurisdiction. The state cannot act outside of its territory without

violating the sovereignty of others. National borders, therefore, confine the power of the

“Leviathan” to a given geographical space; the state’s reach does not extend beyond these

borders. While states can in principle project force to territories where they are not sovereign,

3 Krasner notes that the sovereignty norm is not always perfectly adhered to. States sometime voluntarily contract away their sovereignty and sometimes have their sovereignty unwelcomely impinged upon. However, while Krasner rightly argues against hard notions of sovereignty, violations of the sovereignty principle are exceptional; for most transactions, most of the time, states are sovereign entities.

9

Salehyan

crossing national boundaries—especially with military forces—may provoke a costly interstate

war and international censure. Extending beyond one’s territorial domain violates the

sovereignty principle which in turn invites retaliation, and is therefore costly.

The population of a country, however, can and often does cross national boundaries—the

territoriality norm restricts the movement of military forces but is less constraining with respect

to the movement of people (Andreas 2003). International migration implies that not all

politically-relevant populations reside within the borders of the state where they are subject to

the state’s laws and policing efforts. Migrant diasporas are defined here broadly as populations

who politically identify with a given nation-state, but who do not reside within the territory of

this state. Part of this diaspora, moreover, may be opposed to the regime of their home country.4

As the reasons for migration are varied, not all diasporas or members of a given diaspora are

equally likely to engage in political opposition towards their country of origin, although they

may still identify with the state. 5 Economic migrants leave in search of an improved standard of

living and may or may not oppose their home regime (Fitzgerald 2000). Refugee diasporas, on

the other hand, exit the state because of a direct experience of persecution or political violence

and therefore have a strong motive to oppose the regime from which they fled. Refugee

communities in exile—e.g. Cubans in the U.S., Kurds in Europe, Palestinians in Jordan and

Lebanon, etc—often organize opposition activities and can do so in relative safety as the home

government cannot repress these efforts. Albert O. Hirschman’s (1970) classic distinction

4 Home country, country of origin, and sending country all refer to the country from which the migrants originate. Host country, receiving country, and country of destination all refer to the country to which migrants go. Furthermore, target country will refer to the target of transnational rebel activities—namely, the country of origin. 5 “Diasporas,” “refugee diasporas,” and “trans-national rebels” are distinct categories, that are subsets of one another. Diasporas are defined as people who identify with a nation-state but who do not reside within the territory of this state. Refugee diasporas are a subset of the larger diaspora, and include those whose primary motivation for migration was to escape political violence. Trans-national rebels members of the diaspora who undertake violent actions against their home state. While most trans-national rebels are drawn from refugee communities, not all are; and, not all refugees are members of TNR’s.

10

Salehyan

between “exit” and “voice,” therefore, is not as clear-cut as is often claimed. Rather than exit

and voice being mutually exclusive responses to discontent, refugee diasporas may continue to

be active in their opposition to their home country (Weiner 1992-1993; Zolberg 1989).

Thus, rebel organizations in exile—a subset of the larger diaspora—often use

neighboring territories while they are mobilizing troops and resources, thus placing themselves

outside of the state’s reach. Unless the rebels can locate a safe “incubation” space, early

mobilization efforts while the rebel organization is still weak invite the full coercive response of

the state and are likely to nip the rebellion in the bud. A position beyond the state’s borders

provides such a space; the state cannot easily repress challengers residing abroad. While migrant

diasporas scattered across the world may be involved in a wide variety of political opposition

activities—e.g. creating TV and radio broadcasts, internet sites, channeling funds to opposition

parties, etc—having access to neighboring territory is likely to be especially important for

combatant groups. Rebel armies usually do not have the technology to project force across long

distances. The ability to locate themselves in contiguous territory, therefore, will be especially

important for rebel organizations.

Once fighting is underway, these trans-national rebels (TNR’s) can attack the state from

bases across national boundaries and subsequently escape to safety. Having access to territory

outside of the target state therefore reduces the costs that the government can impose on rebel

groups and provides the opportunity for rebellion. The government is limited in its ability to

pursue rebel groups across the border as doing so necessarily violates the sovereignty of the

neighboring state. The government risks a conflict with the neighboring country and an invasion

of another state’s territory is likely to be seen as illegitimate by the international community. For

these reasons, the state’s “power to hurt” is diminished as it cannot bring all of its forces to bear

11

Salehyan

in crushing an insurgency; therefore even a weak challenger can confront a much stronger

opponent (Slantchev 2003).

The empirical literature hints at such a relationship between international borders and

conflict. Buhaug and Gates (2002) demonstrate that rebellions which occur near a national

boundary tend to be larger in scope than those located closer to the center of the country,

suggesting that borders themselves provide a measure of protection to rebel groups. Further, in

his survey of eleven civil conflicts, I. William Zartman (1992) finds that rebel groups often use

neighboring territory to attack their target government. While these studies lend some support to

notion that external bases may lead to increased levels of conflict, they do not provide definitive

evidence.

In short, rebellion will be more likely to occur when the state’s ability to repress

challengers is reduced or constrained. Importantly, national boundaries place territorial limits on

the state’s police and military capabilities; state forces cannot cross into neighboring countries—

thus violating their sovereignty—without provoking others. Therefore, access to neighboring

territory provides opportunity for rebel groups and creates conditions conducive to civil war.

The Role of the Host State

When (and where) will TNR’s be able to use neighboring countries as a base of operations? It is

unproblematic to assume that for the most part, countries do not wish to have armed insurgents

on their soil, even if their activities are primarily directed at other states. Armed non-state actors

on one’s territory create a security risk and hosting another state’s dissidents jeopardizes bilateral

relations between the target and host countries. Therefore, we must understand the role of the

host government in permitting rebels to operate on their territory.

12

Salehyan

There are two conditions under which neighboring states are more likely to be used by

TNR’s. First, rebels will use state B’s territory in its fight against state A if state B is incapable

of stopping them (Lischer 2003). Poor governments may not be able to adequately restrict the

political activities of diaspora communities and TNR’s, especially if they lack financial, policing,

and infrastructural resources. Given extremely limited resources, poor governments face high

opportunity costs for trying to cope with what is essentially another state’s problem. More

pressing internal political (including repressing domestic insurgents) and economic concerns

may weigh more heavily on the host government’s agenda. Secondly, state B may allow TNR’s

from state A to operate on its territory if states A and B are hostile to one another (Lischer 2003;

Teitelbaum 1984; Weiner 1992; Zartman 1992). Under these conditions, states will use rebels in

a “proxy war” against their rivals, and encourage TNR’s in their efforts. For example, Iran and

Iraq—two long-time rivals—provided sanctuary to one another’s rebel movements. Similarly,

the US aided Cuban exiles in launching the Bay of Pigs invasion.

In comparing these two conditions—lack of capacity versus encouraging TNR’s—we

should expect conflict to be more likely in the latter case. In cases where the host country is

simply too weak to stop TNR’s from operating on their soil, there is no active support of rebel

groups—the state is simply acquiescent. It neither restricts nor assists the TNR group.

Furthermore, the target government may engage in some limited pursuit efforts across the border

in order to attack rebel encampments. The host state will be circumscribed in its abilities to

respond to these incursions by its neighbors and may not strongly object, so long as they are

limited, but more extensive forays into its territory will elicit a more forceful response. On the

other hand, when the host and home countries are rivals, the host state may ally with and

encourage the rebels, and will provide material support. Rival states, moreover, will object to

13

Salehyan

even minor intrusions across the border. Therefore, hostile neighbors yield a bigger risk of civil

war because they provide an even deeper cover for rebel organizations.

Political Opportunities and Bargaining Theory

Increasingly, studies of civil war are borrowing from the international conflict literature which

emphasizes bargaining failure as a key cause of war (Lake 2003; as applied to international

relations see, Fearon 1995; Powell 1999; Slantchev 2003; Wagner 2000). Central to this

framework is that since conflict is costly, actors should in principle be able to reach a bargained

solution short of war that leaves them better off. According to this perspective, there are at least

three important causes of war. First, uncertainty about relative capabilities and incentives to

misrepresent private information about such capabilities may lead actors to incorrectly assess

their probability of victory in a conflict. Second, issues that are indivisible, or at least

imperfectly divisible, make bargaining difficult. Lastly, if actors cannot credibly commit to a

negotiated agreement, the parties may be locked in a situation in which fighting is preferred to

settlement. This perspective can, moreover, be easily transferred to conflict resolution:

continued fighting is costly and will persist until information problems are no longer present,

commitments to peace can be made credible, and/or the issue indivisibilities can be resolved.

When rebel groups are able to locate outside of the state’s boundaries, this should be

reflected in the bargaining situation as the cost/benefit calculations of the parties are altered.

Access to neighboring territory is a structural, permissive condition that affords rebels the

opportunity to fight, but this does not adequately address the bargaining puzzle of why conflicts

begin and continue given the costs. Having an extraterritorial base simply raises the rebel

group’s bargaining power as the government’s probability of outright victory and the costs it can

14

Salehyan

inflict on the rebel group are reduced. Rather than bearing the costs of cross-border attacks—in

which its retaliatory capabilities are constrained—the government should in principle be willing

to offer some concession that will halt these attacks. There should be some negotiated outcome

that is preferable to continued conflict. So why not just reach a suitable settlement and forgo the

costs of fighting?

First, uncertainty about relative capabilities should not be a problem. In the early stages

of conflict, relative capabilities clearly favor the government—the rebel group can demand very

little on the basis of its current capabilities. Over the course of a conflict, the rebel group may

become stronger as it is able to recruit more soldiers, capture resources, purchase armaments,

etc., and the government may be uncertain about the rate of change in these capabilities. Yet

there is a limit to the rebel’s ability to mobilize (resources and troops are not infinitely available)

and information about military capabilities should be quickly revealed on the battlefield (Filson

and Werner 2002; Wagner 2001). If information problems are at the heart of civil war, we

should not see costly, long-term wars (e.g. Sri Lanka, Sudan, Turkey) because conflict itself

reduces informational gaps—but we do se such protracted conflicts. Second, as Fearon (1995)

argues, nearly all goods are divisible, and so issue indivisibility is not a major cause of war. As

the proposed partition of Jerusalem demonstrates, even sacred towns and objects may be subject

to negotiation.

This brings us to the problem of credible commitments, which has been identified as a

major reason why civil conflicts are so difficult to resolve through bargaining (Walter 1997,

2002). As Barbara Walter argues, civil wars are difficult to end through negotiated settlements

because implementing the terms of a peace agreement leaves parties vulnerable to exploitation

and surprise attack. To end a civil conflict, both sides must convincingly demonstrate to one

15

Salehyan

another that they are unwilling and/or unable to fight, which usually requires some form of

disarmament. However, the process of disarmament leaves combatants vulnerable to attack.

There is little assurance that one’s rival will abide by the terms of a peace agreement and not use

this position of weakness to their advantage through a surprise assault. This strategic situation is

akin to the classic Prisoner’s Dilemma in which both sides would be better off by reaching a

deal, but neither can be assured that their opponent will not defect from its terms. Neither side

can be certain that if it does cooperate and disarm, its opponent will not succumb to the

temptation payoff by striking.

In principle, groups may be able to use costly signals to show their resolve for peace, but

in practice, agreements are difficult to make self-enforcing because of the lack of adequate

monitoring mechanisms. Even if the actors agree to disarm simultaneously or through reciprocal

disarmament agreements (i.e., tit-for-tat) informational problems in the context of deep mistrust

make self-enforcing contracts hard to reach. Each side cannot be assured that the other has lived

up to their side of the bargain because it is difficult to verify whether full disarmament has

actually taken place. Hidden weapons caches, for instance, may elude verification schemes. As

Walter (2002: 24-25) writes, “The aftermath of a civil war is filled with ‘noise’—bad

information, conflicting signals, and inadvertent mistakes—that make it difficult to determine

whether a violation has occurred… A combatant is unlikely to have the money, manpower, or

technology to track all the armaments its enemy may want to hide.” Any undetected defection is

not only costly, but can be fatal for the combatants.

As an extension of this theory, I argue that the commitment problem holds and is

intensified when rebel groups have an extraterritorial base. In such circumstances, the

commitment of a third party—the neighboring state—is required. A key component of the rebel

16

Salehyan

group’s ability to fight is its access to neighboring territory, which may be thought of a type of

“weapon;” or, in other words, a means for sustaining the insurgency. “Disarming” must include

commitments to disband extraterritorial bases. The rebel organization cannot credibly commit to

the terms of a peace agreement because there is no assurance that it will not simply take the

benefits offered by the state and continue to maintain its forces abroad with which to reignite the

violence. Having access to neighboring territory is a structural, permissive condition that allows

rebels to sustain a rebellion. In any peace agreement, the combatants must be able to definitively

show that they are no longer willing or able to use force (and “will” is difficult to signal).

However, given the continued option of re-establishing bases across the border, there can be no

guarantee that the rebels will not renege on the deal in the future so long as this permissive

condition, or political opportunity, persists.

Furthermore, even if parties can reach a peace agreement that requires relinquishment of

extraterritorial bases, demobilization is even harder to verify because the rebels are located in

another state’s territory where monitoring is even more complicated. If it is difficult to root out

all weapons stockpiles in one’s own territory, it is even harder to do so in another country.

Verification schemes are more difficult to devise when part of rebels force’s are maintained in

territories that are beyond the state’s jurisdiction and ability to monitor compliance.

As such, peace agreements in wars that have a significant extraterritorial component must

include a third party, the neighboring state, who will be responsible for limiting the activities of

rebel groups and making certain that bases and weapons stockpiles are not being maintained. I

have argued above that having access to neighboring territory is an important factor leading to

the initiation of a civil conflict as well its continuation. Here, I further argue that civil conflicts

will elude resolution until the neighboring state is willing and able to take active measures to

17

Salehyan

control the opposition activities of migrant populations and especially TNR’s operating on its

soil. As long as the host country tacitly or explicitly allows TNR’s to locate on its territory, the

rebel group has an important ‘weapon’ at its disposal. Thus, it is up to the neighboring

government to eliminate the rebel group’s opportunity to fight by effectively ridding its territory

of combatants. However, because the host state may be a rival state or simply too weak to

ensure enforcement, it may not be a reliable partner. Therefore, to end the conflict, the

commitment problem is two-fold. First, the rebel group and the government must credibly

commit to end the violence between themselves. And secondly, the neighboring government

which hosts the TNR group must itself be committed to peace and ensure that insurgent groups

will no longer be able to operate on its soil—the host state must ensure compliance with

demobilization schemes

Thus, when will civil wars end? One possibility is that the rebel group, because it has

benefited from its period of incubation in the neighboring territory, is able to effectively mobilize

to the point of being able to re-enter the state and defeat the government. In such a manner,

Ethiopian and Eritrean rebel groups organized in Sudan and subsequently defeated the Mengistu

regime; and Laurent Kabila’s forces were formed in Rwanda, and later toppled the Mobutu

government in Zaire, to name two prominent examples.

Second, civil wars will elude resolution until the political opportunities leading to conflict

change. Thus, we are more likely to see an end to civil war when conditions in neighboring

states that encourage TNR’s no longer exist. In cases of inter-state rivalry, the neighboring

countries must agree to set aside their differences. Efforts at détente between rival governments

may create the political climate necessary for the host government to limit rebel activities

targeted at neighbors. For example, current peace efforts between India and Pakistan include

18

Salehyan

negotiations over controlling Kashmiri insurgents operating from Pakistani territory. In cases of

neighboring state weakness, the host government must demonstrate that it will devote greater

resources towards restricting the activities of rebel groups on their soil. This may take the form

of policing assistance from the target government, aid from foreign donors and multilateral

agencies, or simply an increase in the central governments resources.

When the rebel group is pushed out of neighboring territories, it loses its insulation from

governmental forces. Therefore, the rebel organization will be more likely to seek a negotiated

settlement to the conflict, and is better able to commit to peace given its lack of a hideout. Peace

settlements will continue to be difficult to reach, but in general, they will be more likely than if

the rebels maintained forces abroad. Alternatively, this lack of a “shield” in neighboring states

leaves the rebel group vulnerable to outright defeat as the state can then apply the full weight of

its forces to the conflict. In either case, civil wars will be more likely to end when these external

factors change.

Preliminary Analysis

To probe the plausibility of the theory, I conduct a preliminary statistical test.6 Most studies of

civil war have treated war onset, duration, and resolution as different research questions. Along

with Elbadawi and Sambanis (2002), I argue that this is not always appropriate; instead, we

should look at the prevalence of civil war. The conditions that initially lead to civil war should

also explain its continuation, and the absence of such conditions should lead to the resolution of

war. Therefore, I argue that neighboring country conditions make civil war more likely to break

out (onset), more likely to continue (duration), and that when conditions change such that TNR’s

6 This is a very tentative probe of the data. It is not meant to be a final set of models, therefore the results must be taken with a grain of salt.

19

Salehyan

no longer have an extraterritorial base, civil wars are more likely to end (resolution). For this

reason, the analysis here focuses on war prevalence.

I consider three main hypotheses with respect to conflict prevalence. First, countries that

border rival states will be more likely to experience civil war. Rival states will allow and even

encourage TNR’s to set up operations on its territory as a tactic against its adversary. Second,

countries that border weak states will be more likely to experience civil war. Weak states will

not be able to restrict the political activities of TNR’s operating on its soil because of their lack

of policing capacity. Lastly, countries that have a large number of refugees in neighboring

countries will be more likely to experience civil war. Refugees are likely to oppose their home

country and will mobilize opposition activities from adjacent states. Refugees are also likely to

be recruited into TNR organizations. The main purpose here is simply to assess whether the

hypotheses are feasible rather than a definitive set of models.

The dependent variable is drawn from the Uppsala University Armed Conflicts dataset

and includes only those conflicts which have reached 1,000 battle deaths in a given year. The

scope of analysis is all civil wars from 1951 to 1999; 1951 is chosen as the start year because

refugee data begins in that year. I use the dataset used in Fearon and Laitin’s (2003) to control

for some of the factors they use. However, instead of simply looking at onset as F&L do, the

models below examine prevalence and are estimated using three different estimation techniques:

random effects probit, dynamic probit, and a Generalized Estimating Equations probit.7 All three

models are used to check the robustness of the findings to various estimation techniques,

according to the suggestion by Elbadawi and Sambanis (2001). Furthermore, dynamic probit

models can account for duration-dependence in the dependent variable.

7 See Elbadawi and Sambanis for a discussion of the desirability and relative merits of these models for estimating the prevalence of civil war. See also Zorn (2001) for a discussion of Generalized Estimation Equations model.

20

Salehyan

I include four of my own variables to test my hypotheses. First, I created a variable for

weak neighboring states. To do so I constructed a dichotomous variable coded one if the country

of observation borders at least one state that falls below the 25th percentile on the Correlates of

War capabilities index (CINC) for the given year (zero otherwise).8 This data is an index of

state capabilities which includes measures of economic development (e.g. electricity

consumption) and military resources (e.g. military expenditures).9 Second, I included a variable

coded one if at least one neighboring country is experiencing a civil war itself, which is included

as a further indicator of a ‘weak state.’

Third, I created a variable for rival neighboring states. To do so I constructed another

dichotomous variable coded one if the country borders at least one state for which the dyadic

Tau-B score is negative, indicating that the two countries are members of opposing alliances.

Tau-B compares alliance portfolios between states and ranges from -1 (complete opposition) to

positive 1 (complete accordance). The CINC data and the Tau-B data were obtained using the

EUgene software package10. Finally, I include data from the UNHCR on the total number

refugees from the origin state (logged) that are in all neighboring states. Because refugees are

endogenous to conflict, that is, they are a result of conflict as well as a possible cause, current

refugee figures would not be appropriate. To eliminate some of this endogeneity, I worked with

various lags of the refugee variable.

The controls used in this preliminary analysis come from Fearon and Laitin’s (2003)

dataset and include GDP, ethnic fractionalization, political instability, and the Polity score and its 8 For each year (1946-1999) I used the STATA “summ” command to identify the cutoff point for the bottom quartile. Countries that are below this point for the given year are given a 1 value. 9 Singer, J. David, Stuart Bremer, and John Stuckey. 1972. "Capability Distribution, Uncertainty, and Major Power War, 1820-1965." in Bruce Russett, ed. Peace, War and Numbers. Beverly Hills: Sage. See also: Bennett, D. Scott, and Allan Stam. 2000. “EUGene: A Conceptual Manual.” International Interactions 26:179-204. 10 Bennett, D. Scott and Allan Stam. 2000. “EUgene: A Conceptual Manual.” International Interactions. 26:179-204.

21

Salehyan

squared term. Political instability is a dummy variable indicating a change of 3 or more in the

Polity index.11 GDP is expected to decrease the likelihood of conflict while political instability

and ethnic fractionalization should increase it. The relationship with the Polity score is expected

to be non-monotonic: mid-level Polity scores are expected to increase the probability of conflict

while values at the low and high end of the Polity index should decrease conflict.

Results

The first model (Table 1) is a random effects probit analysis on conflict incidence. This model

shows that countries bordering rival states (rival) are significantly more likely to experience civil

war, confirming the hypothesis that hostile governments are likely to support rebel movements.

The coefficient on weak neighboring states (weak) is not in the expected direction, and is not

statistically significant. Weak states, as measured by values of the CINC index do not appear to

have a positive effect on the likelihood of conflict. In the future, better measures of state

weakness will be included. The other measure of neighboring state weakness considered

whether the neighboring state is involved in a civil conflict of its own (nbconflict). This

indicator of state weakness is significant and in the expected direction, indicating that “failed

states”—or states which experience domestic turmoil—are likely to be used by transnational

rebel groups as well.

To estimate the effects of refugees, I include two lagged values of the refugee stock in

neighboring countries. Including current values of refugees would not be appropriate as these

refugees are likely to stem from the current conflict and are endogenous. A once lagged value of

refugees may also be suspect if migrants leave because they expect conflict in the near future.

Therefore, I include the second and third lag of the refugee variable (l2ref and l3ref) to limit 11 See Fearon and Laitin (2003) for a full description of the data.

22

Salehyan

some of the endogeneity associated with this indicator. Inclusion of further lagged values do not

come up significant. As expected, lagged values of refugees in neighboring countries positively

affect current conflict. Thus, yesterday’s refugees are likely to become involved in today’s

conflicts.

Of the control variables, the Polity index demonstrates the expected parabolic

relationship between democracy and civil conflict. Also as expected, ethnic fractionalization and

political instability increase the likelihood of conflict while wealth decreases it.

TABLE 1: RANDOM EFFECTS PROBIT REGRESSION

Random-effects probit regression Number of obs = 5889

Group variable (i): ccode Number of groups = 155

Random effects u_i ~ Gaussian Obs per group: min = 4

avg = 38.0

max = 51

Wald chi2(10) = 271.66

Log likelihood = -941.14831 Prob > chi2 = 0.0000

------------------------------------------------------------------------------

conflict | Coef. Std. Err. z P>|z| [95% Conf. Interval]

-------------+----------------------------------------------------------------

rival | .4960532 .1074222 4.62 0.000 .2855096 .7065969

weak | -.0115564 .086116 -0.13 0.893 -.1803407 .157228

l2ref | .0532208 .0080979 6.57 0.000 .0373493 .0690923

l3ref | 6.05e-07 1.65e-07 3.66 0.000 2.81e-07 9.28e-07

nbconflict | .5135962 .0903648 5.68 0.000 .3364846 .6907079

polity2l | .0115914 .006734 1.72 0.085 -.0016069 .0247898

politysq | -.006476 .0015214 -4.26 0.000 -.0094579 -.0034941

ethfrac | .6271564 .1977895 3.17 0.002 .2394961 1.014817

gdpenl | -.071427 .0246812 -2.89 0.004 -.1198012 -.0230527

instab | .3029056 .0901218 3.36 0.001 .1262701 .4795411

_cons | -2.754602 .2110621 -13.05 0.000 -3.168276 -2.340927

-------------+----------------------------------------------------------------

/lnsig2u | .1626078 .1535389 -.138323 .4635385

-------------+----------------------------------------------------------------

sigma_u | 1.0847 .0832719 .933176 1.260829

rho | .5405626 .0381321 .4654743 .6138533

------------------------------------------------------------------------------

Likelihood-ratio test of rho=0: chibar2(01) = 417.67 Prob >= chibar2 = 0.000

23

Salehyan

The second model is Generalized Estimating Equations model (table 2). This model is

population-averaged rather than including random effects. The advantage of the GEE model is

that allows an AR(1) process and robust standard errors (Zorn 2001). The results are generally

consistent with the random-effects probit specification. States with rivals on their borders are

more likely to experience civil conflict, although the statistical significance of this indicator is

slightly reduced. In this model, in contrast to the random-effects probit model, the coefficient on

weak is now in the expected direction, although it is still not statistically significant. The other

indicator of state weakness, nbconflict, is again positive and significant further providing

evidence that states with neighbors at civil war are more likely to experience conflict themselves.

Finally, the lagged indicators of the refugee variable are also in the expected direction and

significant.

24

Salehyan

TABLE 2: GEE POPULATION AVERAGED MODEL, AR(1)

GEE population-averaged model Number of obs = 5671 Group and time vars: ccode year Number of groups = 149

Link: probit Obs per group: min = 4

Family: binomial avg = 38.1

Correlation: AR(1) max = 51

Wald chi2(10) = 111.48

Scale parameter: 1 Prob > chi2 = 0.0000

(standard errors adjusted for clustering on ccode)

------------------------------------------------------------------------------

| Semi-robust

conflict | Coef. Std. Err. z P>|z| [95% Conf. Interval]

-------------+----------------------------------------------------------------

rival | .2173144 .1285618 1.69 0.091 -.0346621 .4692909

weak | .1209714 .1211657 1.00 0.318 -.116509 .3584517

l2ref | .0404131 .0135373 2.99 0.003 .0138804 .0669458

l3ref | 5.74e-07 1.57e-07 3.66 0.000 2.66e-07 8.82e-07

nbconflict | .2184243 .0699389 3.12 0.002 .0813465 .3555021

polity2l | .0125312 .0083238 1.51 0.132 -.0037832 .0288456

politysq | -.0031077 .0020473 -1.52 0.129 -.0071204 .000905

ethfrac | .6069912 .2555179 2.38 0.018 .1061853 1.107797

gdpenl | -.0786801 .0311247 -2.53 0.011 -.1396834 -.0176768

instab | -.0032239 .0879299 -0.04 0.971 -.1755632 .1691155

_cons | -1.925522 .2412693 -7.98 0.000 -2.398401 -1.452643

The final model is a dynamic probit. A dynamic probit specification is able to capture duration-

dependence in the data. In other words, a dynamic probit model is able to account for the history

of conflict and peace in the country. It is likely the case that states with a history of peace are

likely to stay at peace while states with a history of conflict are more likely experience conflict in

the subsequent period. To estimate a dynamic probit model, I include lagged values of the

dependent variable in addition to interaction terms between the lagged dependent variable and all

of the independent variables. Again, the results generally conform to those above. Rival is

positive although marginally significant at the .05 level on a one-tailed test. The variable weak is

25

Salehyan

again not found to be significant. Nbconflict retains its significance as does the twice lagged

value of refugees. The third lag of refugees is not significant in this model, however.

TABLE 3: DYNAMIC PROBIT

Probit estimates Number of obs = 5889

LR chi2(21) = 1748.75

Prob > chi2 = 0.0000

Log likelihood = -647.01349 Pseudo R2 = 0.5747

------------------------------------------------------------------------------

conflict | Coef. Std. Err. z P>|z| [95% Conf. Interval]

-------------+----------------------------------------------------------------

rival | .1724974 .106334 1.62 0.105 -.0359134 .3809083

weak | .0994394 .0939955 1.06 0.290 -.0847884 .2836673

l2ref | .0415287 .0103659 4.01 0.000 .021212 .0618455

l3ref | 3.26e-07 3.29e-07 0.99 0.321 -3.19e-07 9.71e-07

nbconflict | .3136597 .0981159 3.20 0.001 .1213561 .5059633

polity2l | .00609 .0070944 0.86 0.391 -.0078147 .0199948

politysq | -.0035836 .0016743 -2.14 0.032 -.0068652 -.000302

ethfrac | .1771093 .162666 1.09 0.276 -.1417102 .4959287

gdpenl | -.0198973 .0181619 -1.10 0.273 -.055494 .0156995

instab | .2167834 .1099094 1.97 0.049 .0013649 .4322018

ldv | 2.876271 .3541844 8.12 0.000 2.182083 3.57046

ldvrival | -.1367458 .2222905 -0.62 0.538 -.5724271 .2989355

ldvweak | -.1366155 .1885252 -0.72 0.469 -.5061181 .232887

ldvl2ref | -.0268061 .017955 -1.49 0.135 -.0619972 .0083851

ldvl3ref | -1.30e-07 3.78e-07 -0.34 0.730 -8.72e-07 6.11e-07

ldvnbconf | -.071707 .1963169 -0.37 0.715 -.4564811 .313067

ldvpolity | .0010007 .0154265 0.06 0.948 -.0292346 .031236

ldvpolitysq | -.0016745 .0035075 -0.48 0.633 -.0085491 .0052002

ldvethfrac | .7633341 .3376648 2.26 0.024 .1015232 1.425145

ldvgdp | -.0829548 .052343 -1.58 0.113 -.1855452 .0196356

ldvinstab | -.5123978 .2012016 -2.55 0.011 -.9067457 -.1180499

_cons | -2.435364 .1641489 -14.84 0.000 -2.75709 -2.113638

------------------------------------------------------------------------------

In sum, there is good evidence supporting the three main hypotheses. The first hypothesis that

countries with contiguous rivals are more likely to experience civil war is supported by the data.

26

Salehyan

The statistical confidence in this finding is higher in the random-effects probit model than in the

other two specifications, but in general it is robust to various modeling choices. I have argued

that this effect is due to the provision of sanctuary to rebel groups. Thus, Iraq hosted rebels from

Iran, the Mojahedin-e-Khalq; Pakistan hosted Kashmiri and Punjabi insurgents from India; and

Honduras hosted the Contra rebels from Nicaragua.

The second hypothesis, that civil wars are more likely within states that have neighbors

who are incapable of stopping transnational rebel groups finds mixed support. The first indicator

of state weakness, as measured by the CINC index, does not come up significant in any of the

models. In the future, alternative indicators will be considered. The second indicator of state

weakness, civil conflict in neighboring states, finds strong support across all three models. I

argue that when neighboring states are preoccupied with suppressing their own rebels, their

territory is likely to be used by rebels from across the border. In such manner, Rwandan rebel

groups located in Uganda and DR Congo have thrived. Similarly, southern Sudan has been a

haven for Ethiopian rebel groups and vice-versa.

The final hypothesis that refugee groups in neighboring countries are likely to contribute

to violence is also strongly supported by the data. Lagged values of refugee stocks in

neighboring countries show a robust relationship between communities in exile and current

violence. Thus, populations located outside of the boundaries of the state often support rebel

groups. As such, Palestinian refugees have contributed to violence in Israel and the West Bank;

refugees from Western Sahara residing in Algeria have engaged in conflict; and Liberian

refugees have organized into armed factions, to name a few examples.

27

Salehyan

References: Andreas, Peter. 2003. “Redrawing the Line: Borders and Security in the Twenty-First Century.” International Security 28:78-111. Brogan, Patrick. 1998. World Conflicts: A Comprehensive Guide to World Strife Since 1945. Lanham, MD: Scarecrow Press. Brown, Michael E. (Ed.). 1996. The International Dimensions of Internal Conflict. Cambridge, MA: MIT Press. Buhaug, Halvard, and Scott Gates. 2002. “The Geography of Civil War.” Journal of Peace Research 39:417–33. Collier, Paul and Anke Hoeffler. 2001. “Greed and Grievance in Civil War.” Unpublished Working Paper. World Bank. Elbadawi, Ibrahim, and Nicholas Sambanis. 2002. “How Much War Will We See?: Explaining the Prevalence of Civil War.” Journal of Conflict Resolution 46:307-34. Fearon, James D. 1995. “Rationalist Explanations for War.” International Organization 49:379-414. Fearon, James D., and David D. Laitin. 2003. “Ethnicity, Insurgency, and Civil War.” American Political Science Review 97:75-90. Filson, Darren, and Suzanne Werner. 2002. “A Bargaining Model of War and Peace: Anticipating the Onset, Duration, and Outcome of War.” American Journal of Political Science 46:819-38. Fitzgerald, David. 2000. Negotiating Extraterritorial Citizenship: Mexican Migration and the Transnational Politics of Community. La Jolla, CA: Center for Comparative Immigration Studies. Gleditsch, Kristian S. 2002. All International Politics is Local: The Diffusion of Conflict, Integration, and Democratization. Ann Arbor, MI: University of Michigan Press. Gurr, Ted R. 1970. Why Men Rebel. Princeton, NJ: Princeton University Press. Gurr, Ted R., and Will H. Moore. 1997. “Ethnopolitical Rebellion: A Cross-sectional Analysis of the 1980s with Risk Assessments for the 1990s.” American Journal of Political Science 41:1079-103. Hegre, Håvard, Tanja Ellingsen, Scott Gates, and Nils Petter Gleditsch. 2001. “Toward a Democratic Civil Peace? Democracy, Political Change, and Civil War, 1816–1992.” American Political Science Review 95:33–48.

28

Salehyan

Hirschman, Albert O. 1970. Exit, Voice, and Loyalty: Responses to Decline in Firms, Organizations, and States. Cambridge, MA: Harvard University Press. Jackson, Robert H. 1987. “Quasi-states, Dual Regimes, and Neoclassical Theory: International Jurisprudence and the Third World.” International Organization 41:519-49. Krasner, Stephen. 1995-1996. “Compromising Westphalia.” International Security 20:115-51. Kratochwil, Friedrich. 1986. “Of Systems, Boundaries, and Territoriality: An Inquiry Into the Formation of the State System.” World Politics 39:27-52. Lake, David. 2003. “International Relations Theory and Internal Conflict: Insights from the Interstices.” International Studies Review 5:81-9. Lake, David A., and Donald Rothchild (Eds.). 1998. The International Spread of Ethnic Conflict. Princeton, NJ: Princeton University Press. Lichbach, Mark I. 1995. The Rebel's Dilemma. Ann Arbor, MI: Michigan University Press. Lischer, Sarah Kenyon. 2003. “Collateral Damage: Humanitarian Assistance as a Cause of Conflict.” International Security 28:79-109. Midlarsky, Manus (Ed.). 1992. The Internationalization of Communal Strife. New York, NY: Routledge. Muller, Edward N., and Mitchell A. Seligson. 1987. “Inequality and Insurgency.” American Political Science Review 87:425-51. Muller, Edward N., and Erich Weede. 1990. “Cross-National Variation in Political Violence: A Rational Action Approach.” Journal of Conflict Resolution 34:624-51. Posen, Barry. 1993. “The Security Dilemma and Ethnic Conflict.” Survival 35:27-47. Powell, Robert. 1999. In the Shadow of Power: States and Strategies in International Politics. Princeton, NJ: Princeton University Press. Ruggie, John Gerard. 1993. “Territorality and Beyond: Problematizing Modernity in International Relations.” International Organization 47:139-74. Slantchev, Branislav. 2003. “The Power to Hurt: Costly Conflict with Completely Informed States.” American Political Science Review 97:123-33. Teitelbaum, Michael. 1984. “Immigration, Refugees, and Foreign Policy.” International Organization 38:429-50.

29

Salehyan

Tilly, Charles. 1978. From Mobilization to Revolution. Reading, MA: Addison-Wesley. Wagner, R. Harrison. 2000. “Bargaining and War.” American Journal of Political Science 44:469-84. Walter, Barbara F. 1997. “The Critical Barrier to Civil War Settlement.” International Organization 51:335-64. Walter, Barbara F. 2002. Committing to Peace: The Successful Resolution of Civil Wars. Princeton, NJ: Princeton University Press. Weiner, Myron. 1992-1993. “Security, Stability, and International Migration.” International Security 17:91-126. Zacher, Mark. 2001. “The Territorial Integrity Norm: International Boundaries and the use of Force.” International Organization 55:215-50. Zartman, I. William. 1992. “The Internationalization of Communal Strife: Temptations and Opportunities of Triangulation.” In The Internationalization of Communal Strife, edited by Manus Midlarski, New York: Routledge. Zolberg, Aristide, Astri Suhrke, and Sergio Aguayo. 1989. Escape from Violence: Conflict and the Refugee Crisis in the Developing World. New York: Oxford University Press. Zorn, Christopher. 2001. “Generalized Estimating Equation Models for Correlated Data: A Review With Applications.” American Journal of Political Science 45:470-90.

30