American Political Science Review
Vol. 97, No. 1   February 2003
Ethnicity, Insurgency, and Civil War
JAMES D. FEARON and DAVID D. LAITTN  Stanford University
A n influential conventional wisdom holds that civil wars proliferated rapidly with the end of /1   the Cold War and that the root cause of many or most of these has been ethnic and religious
A antagonisms. We show that the current prevalence of internal war is mainly the result of a steady accumulation of protracted conflicts since the 1950s and 1960s rather than a sudden change associated with a new, post-Cold War international system. We also find that after controlling for per capita income, more ethnically or religiously diverse countries have been no more likely to experience significant civil violence 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. 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—which marks financially and bureaucratically weak states and also favors rebel recruitment—political instability, rough terrain, and large populations.
Between 1945 and 1999, about 3.33 million battle deaths occurred in the 25 interstate wars that killed at least 1,000 and had at least 100 dead on each side. These wars involved just 25 states that suffered casualties of at least 1,000 and had a median duration of not quite 3 months. In contrast, in the same period there were roughly 127 civil wars that killed at least 1,000, 25 of which were ongoing in 1999. A conservative estimate of the total dead as a direct result of these conflicts is 16.2 million, five times the interstate toll. These civil wars occurred in 73 states—more than a third of the United Nations system—and had a median duration of roughly six years.1 The civil conflicts in this period surely produced refugee flows far greater than their death toll and far greater than the refugee flows associated with interstate wars since 1945. Cases such as Afghanistan, Somalia, and Lebanon testify to the economic devastation that civil wars can produce. By these crude measures, civil war has been a far greater scourge than interstate war in this period, though it has been studied far less.
What explains the recent prevalence of violent civil conflict around the world? Is it due to the end of the Cold War and associated changes in the international system, or is it the result of longer-term trends? Why have some countries had civil wars while others have not? and Why did the wars break out when they did? We address these questions using data for the period 1945 to 1999 on the 161 countries that had a population of at least half a million in 1990.
James D. Fearon and David D. Laitin are Professors, Department of Political Science, Stanford University, Stanford, CA 94305-6044 (jfearon@stanford.edu and dlaitin@stanford.edu).
We wish to thank the many people who provided comments on earlier versions of this paper in a series of seminar presentations. The authors also gratefully acknowledge the support of the National Science Foundation (Grants SES-9876477 and SES-9876530); support from the Center for Advanced Study in the Behavioral Sciences with funds from the William and Flora Hewlett Foundation; valuable research assistance from Ebru Erdem, Nikolay Marinov, Quinn Mecham, David Patel, and TQ Shang; sharing of data by Paul Collier. 1 The interstate war data derive from Singer and Small 1994, updated to include the Kargil and Eritrean wars. The bases for the civil war estimates are discussed below.
The data cast doubt on three influential conventional wisdoms concerning political conflict before and after the Cold War. First, contrary to common opinion, the prevalence of civil war in the 1990s was not due to the end of the Cold War and associated changes in the international system. The current level of about one in six countries had already been reached prior to the breakup of the Soviet Union and resulted from a steady, gradual accumulation of civil conflicts that began immediately after World War II.
Second, it appears not to be true that a greater degree of ethnic or religious diversity—or indeed any particular cultural demography—by itself makes a country more prone to civil war. This finding runs contrary to a common view among journalists, policy makers, and academics, which holds "plural" societies to be especially conflict-prone due to ethnic or religious tensions and antagonisms.
Third, we find little evidence that one can predict where a civil war will break out by looking for where ethnic or other broad political grievances are strongest. Were this so, one would expect political democracies and states that observe civil liberties to be less civil war-prone than dictatorships. One would further anticipate that state discrimination against minority religions or languages would imply higher risks of civil war. We show that when comparing states at similar levels of per capita income, these expectations are not borne out.
The main factors determining both the secular trend and the cross-sectional variation in civil violence in this period are not ethnic or religious differences or broadly held grievances but, rather, conditions that favor insurgency. Insurgency is a technology of military conflict characterized by small, lightly armed bands practicing guerrilla warfare from rural base areas. As a form of warfare insurgency can be harnessed to diverse political agendas, motivations, and grievances. The concept is most closely associated with communist insurgency, but the methods have equally served Islamic fundamentalists, ethnic nationalists, or "rebels" who focus mainly on traffic in coca or diamonds.
We hypothesize that financially, organizationally, and politically weak central governments render insurgency more feasible and attractive due to weak local
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policing or inept and corrupt counterinsurgency practices. These often include a propensity for brutal and indiscriminate retaliation that helps drive noncombat-ant locals into rebel forces. Police and counterinsurgent weakness, we argue, is proxied by a low per capita income. Shocks to counterinsurgent capabilities can arise from political instability at the center or the sudden loss of a foreign patron. On the rebel side, insurgency is favored by rough terrain, rebels with local knowledge of the population superior to the government's, and a large population. All three aid rebels in hiding from superior government forces. Foreign base camps, financial support, and training also favor insurgency.
Our data show that measures of cultural diversity and grievances fail to postdict civil war onset, while measures of conditions that favor insurgency do fairly well. Surely ethnic antagonisms, nationalist sentiments, and grievances often motivate rebels and their supporters. But such broad factors are too common to distinguish the cases where civil war breaks out. Also, because insurgency can be successfully practiced by small numbers of rebels under the right conditions, civil war may require only a small number with intense grievances to get going.
Using data on about 45 civil wars since 1960, Collier and Hoeffler (1999, 2001) find similarly that measures of "objective grievance" fare worse as predictors than economic variables, which they initially interpreted as measures of rebel "greed" (i.e., economic motivation).2 More recently, they argue that rebellion is better explained by "opportunity" than by grievance (cf. Eisinger 1973 and Tilly 1978) and that the main determinant of opportunity is the availability of finance and recruits for rebels. They proxy these with measures of primary commodity exports and rates of secondary-school enrollment for males. We agree that financing is one determinant of the viability of insurgency. We argue, however, that economic variables such as per capita income matter primarily because they proxy for state administrative, military, and police capabilities. We find no impact for primary commodity exports, and none for secondary schooling rates distinct from income. Our theoretical interpretation is more Hobbesian than economic. Where states are relatively weak and capricious, both fears and opportunities encourage the rise of would-be rulers who supply a rough local justice while arrogating the power to "tax" for themselves and, often, for a larger cause.
CIVIL WAR SINCE 1945
Building on similar efforts by other civil war researchers,3 we constructed a list of violent civil conflicts
2 There are 79 wars in their sample, but they lose about 34 due to missing values on explanatory variables, which are mainly economic. Standard economic data tend to be missing for countries that are poor and civil war-torn. This highly nonrandom listwise deletion may account for some of the differences between our results.
3 In particular, Doyle and Sambanis (2000), Esty et al. (1998), Gleditsch et al. (2002), the Institute for International and Strategic Studies (2000), Licklider (1995), Singer and Small (1994), Sivard (1996), and Valentino (2002).
that we presently believe to meet the following primary criteria. (1) They involved fighting between agents of (or claimants to) a state and organized, nonstate groups who sought either to take control of a government, to take power in a region, or to use violence to change government policies. (2) The conflict killed at least 1,000 over its course, with a yearly average of at least 100. (3) At least 100 were killed on both sides (including civilians attacked by rebels). The last condition is intended to rule out massacres where there is no organized or effective opposition.4
These criteria are broadly similar to those stated by the Correlates of War (COW) project, Doyle and Sambanis (2000), and several others. We developed our own list (working from these and other sources) mainly because we wanted data for the whole 1945-99 period and because of doubts about particular inclusions and exclusions in each list.5
In one respect our data differ significantly from most others: We see no reason in principle to exclude anti-colonial wars, such as the French versus the National Liberation Front (FLN) in Algeria. We count these as occuring within the colonial empire. Thus, the French state/empire looks highly civil war-prone by our list, with six colonial wars occuring in the 1950s. But to drop such cases would be like dropping the current conflict in Chechnya as a civil war in Russia if the Chechens succeed in gaining independence. Alternatively, it would make even less sense to include them as wars within "states" that did not exist (such as "Algeria" in 1954).
There are both practical and theoretical considerations pointing the other way, however. In practical terms, to include the anticolonial wars in the analysis requires that we form estimates of possible explanatory factors for whole empires, such as gross domestic product (GDP) per capita, ethnic fractionalization, and democracy scores. Further, these estimates must change almost by year, as the colonial empires gradually diminished in size. We are able to use country-level data to produce such estimates for ethnic fractionalization, but our estimates for per capita income are more
4 We used the following secondary criteria to deal with several other coding issues. (4) The start year is the first year in which 100 were killed or in which a violent event occurred that was followed by a sequence of actions that came to satisfy the primary criteria. (5) If a main party to the conflict drops out, we code a new war start if the fighting continues (e.g., Somalia gets a new civil war after Siad Barre is defeated in 1991). (6) War ends are coded by observation of a victory, wholesale demobilization, truce, or peace agreement followed by at least two years of peace. (7) Involvement by foreign troops does not disqualify a case as a civil war for us, provided the other criteria are satisfied. (8) We code multiple wars in a country when distinct rebel groups with distinct objectives are fighting a coherent central state on distinct fronts with little or no explicit coordination. (9) If a state seeks to incorporate and govern territory that is not a recognized state, we consider it a "civil war" only if the fighting continues after the state begins to govern the territory (thus, Indonesia/East Timor 1975, yes, and India/Hyderabad 1947, no).
5 Sambanis (2002) discusses a number of conceptual and operational ambiguities and problems with the COW civil war data. Collier and Hoeffler (2001) base their list on COW data, breaking a number of COW civil wars into multiple wars according to unspecified criteria and including some colonial wars (coded in nonexistent "states," such as Angola 1961) but not others.
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problematic and the question of how to code the empires on a democracy index is vexed. Regarding theory, the colonial empires differed so radically from other independent states, and faced such an inhospitable international environment after the war (with pressure from the United States and the new United Nations system), that we need to be cautious about any empirical results that depend wholly on these cases. Thus we analyze the data both with and without the anticolonial wars.
Descriptive Statistics
We identified 127 conflicts that meet the above criteria, of which 13 were anticolonial wars.6 This makes for 127 civil war starts in a sample of 6,610 country years, a rate of 1.92 per 100. The periods following major international systemic change had the highest onset rates. Civil wars broke out in the late 1940s and the 1950s at 4.6 and 2.2 per 100 country-years, respectively, followed by the 1990s, at 2.0. In absolute terms, the largest number of civil wars began in the 1990s (31), followed by the 1960s and 1970s (19 and 25, respectively).
Omitting the anticolonial conflicts, most civil wars occurred in sub-Saharan Africa (34) and Asia (33), followed by North Africa/the Middle East (17), Latin America (15), Eastern Europe and the former Soviet Union (13), and "the West" (2). The rate of outbreak was highest in Asia, at three per 100 country-years; Africa, North Africa/the Middle East, and Latin America all had rates of about two per 100 country-years. "France," Indonesia, and the Soviet Union/
6 See Fearon and Laitin 2003 for a list of the conflicts.
Russia are the most civil war-prone countries in the sample, with six onsets each.7
Trends over Time
Figure 1 shows the number of countries with ongoing civil wars by year from 1945 to 1999. Since the number of independent states grew sharply in this period, it also shows the proportion of countries with at least one ongoing war in each year.
The graph indicates that, contrary to popular belief, the prevalence of civil wars in the 1990s is not due to effects of the end of the Cold War. The 1999 level of 25 ongoing wars had already been reached by the mid 1980s. Conflicts associated with the Soviet collapse were partly responsible for the sharp increase in the early 1990s, but a marked decline has followed.8
One might conjecture that more and more civil wars are breaking out over time, thus producing the secular increase. This is incorrect. The rate of outbreak is 2.31 per year since 1945, highly variable but showing no significant trend up or down. The secular increase stems from the fact that civil wars have ended at a rate of only about 1.85 per year. The result has been a steady, almost-linear accumulation of unresolved conflicts since 1945.
Put differently, states in the international system have been subject to a more or less constant risk
7 Four outbreaks are coded in the Soviet Union in 1946, in the Baltics and Ukraine, plus Russia's two Chechen wars in the 1990s.
8 Gurr (2000) notes the late-1990s decline in ethnic war and argues that the trend reflects improved management strategies by states and international organizations. The basic pattern in Figure 1 is not an artifact of the way we have coded "civil war"; it is observed in a broad range of other data sets on violent domestic conflict for this period (e.g., Gleditsch et al. 2002).
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of violent civil conflict over the period, but the conflicts they suffer have been difficult to end. The average duration of the civil wars in progress has increased steadily from two years in 1947 to about 15 years in 1999. From a policy perspective this suggests caution about seeing as a temporary "blip" the sorts of military and political problems Western foreign policy makers have faced recently in Kosovo, Macedonia, Bosnia, Somalia, Haiti, East Timor, Colombia, and elsewhere.
ETHNICITY, DISCRIMINATION, AND GRIEVANCES
During the Cold War, political scientists and sociologists often sought to trace rebellion to economic inequality (Muller 1985; Paige 1975; Russett 1964), to rapid economic growth said to destabilize traditional rural social systems (Huntington 1968; Scott 1976), or to frustrations arising from the failure to gain expected benefits of economic modernization (Gurr 1971). A few scholars argued that the real source of rebellion was often ethnic nationalism (Connor 1994), and a rich literature on the sources nationalist mobilization developed in comparative politics (e.g., Anderson 1983, Deutsch 1953, and Gellner 1983). With the collapse of the Soviet Union and Yugoslavia, such culturalist perspectives became a dominant frame for interpreting inter- and intranational conflict (e.g., Huntington 1996).
Using a broad brush, we can distinguish between perennialist and modernist (or constructivist) positions on the nature and sources of ethnic nationalism. Given in purest form by nationalist politicians and journalists reporting on nationalist conflicts in progress, perennialist arguments stress long-standing cultural practices said to define and distinguish ethnic groups. Differences between these practices are argued to have made conflict more likely. Academics rarely make such arguments as baldly as do nationalist leaders. But authors who stress the long-standing, "deep" nature of ethnic differences and suggest that these make domestic peace difficult include Huntington (1996), Ignatieff (1993), Moynihan (1993), Rabushka and Shepsle (1972), and Smith (1986). Arguably, the main message of Horowitz's (1985) influential book on ethnic conflict is that plural societies face a host of pathologies that render them especially prone to conflict and, at the extreme, violence.
In contrast, modernist theories see the thoroughgoing politicization of cultural difference that ethnic nationalism represents as a development of the last 200 to 500 years. The core argument is that economic modernization and the development of the modern state make upward social mobility possible, but contingent on sharing the culture of the group that dominates state or society. When the state or society poses ascrip-tive barriers to upward mobility for minority groups, they may develop separatist nationalist movements: All the more so, according to Anderson (1983), Deutsch (1953), and Gellner (1983), the greater the preexisting cultural differences between the minority group and
the dominant group. (When preexisting differences are slight, assimilation is more likely.)
The two approaches thus imply the same hypothesis about the relationship between cultural diversity and civil conflict.
H\: Measures of a country's ethnic or religious diversity should be associated with a higher risk of civil war.
Seeking to explain anticolonial nationalist movements in countries barely affected by economic modernization, Gellner (1983, 108, nl) argued that even "the advance shadow" of modernization was sufficient to start nationalist dynamics in motion. For Anderson, nationalism quickly became a "modular form" that could be easily "pirated," even under conditions quite different from those during its origination. Nonetheless, if one took the modernist approach literally one might infer that more modernization should imply more discrimination and thus more nationalist contention in culturally divided countries.
Hi'- The effect of ethnic diversity on the probability of civil war should increase at higher levels of per capita income (a proxy for economic modernization).
Horowitz (1985) and several others argue that the relationship between ethnic diversity and severe ethnic conflict is nonmonotonic, with less violence for highly homogeneous and highly heterogeneous countries. The politics of a highly diverse country might be strategically similar to those of a homogeneous one, since small ethnic groups must join coalitions to have political influence, and there are many possibilities for cross-cutting and shifts in coalition membership. Horowitz suggests that the most severe ethnic conflicts will arise in countries where a substantial ethnic minority faces an ethnic majority that can, given ethnic voting, win for sure in any national election. Such arguments yield the following hypothesis.
Fk: Countries with an ethnic majority and a significant ethnic minority are at greater risk for civil war.
We consider several measures for these concepts. For H\ we use (1) the commonly employed ethnolinguis-tic fractionalization (ELF) index based on data from Atlas Narodov Mira 1964, which gives the probability that two randomly drawn individuals in a country are from different ethnolinguistic groups;9 (2) a measure of the share of population belonging to the largest ethnic group that we constructed from the CIA Factbook and other sources (Fearon 2002); (3) the number of distinct languages spoken by groups exceeding 1 % of
9 For this and several other variables we filled in values for missing country years whenever possible based on our own research; often the sources were the CIA Factbook, Encyclopedia Brittanica, and the Library of Congress Country Studies, though we used country-specific sources when necessary.
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the country's population, based on Grimes and Grimes 1996; and (4) a measure of religious fractionalization (analogous to the ELF) that we constructed using data from the CIA Factbook and other sources. For H2 we interact these measures with per capita income. For Fk, we use a dummy variable marking the 74 countries whose largest and second-largest ethnic groups exceed 49% and 7% of the population, respectively. 0
The mechanism that gives rise to nationalist contention in modernist arguments is state or societal discrimination along the lines of cultural difference, which is thought to create the grievances that motivate rebellions. Grievances are difficult to measure independently of our knowledge of the actions we are trying to explain (rebellions, civil war), but measures of average levels of discrimination are feasible. Other things being equal, political democracy should be associated with less discrimination and repression along cultural or other lines, since democracy endows citizens with a political power (the vote) they do not have in dictatorships. Even more directly, measures of state observance of civil rights such as freedom of association, expression, and due process should be associated with less repression and thus lower grievances. State policies that discriminate in favor of a particular group's language or religion should be associated with greater minority grievances. Finally, it is often argued that greater economic inequality creates broad grievances that favor civil conflict (e.g., Muller 1985). Thus, we have the following hypotheses.
H4: Measures of political democracy and civil liberties should be associated with lower risks of civil war onset.
H$: Policies that discriminate in favor of a particular language or religion should raise the risk of civil war onset in states with religious or linguistic minorities.
Greater income inequality should be associated with higher risks of civil war onset.
We consider both the Polity IV and the Przeworski et al. 2000 democracy measures, along with the Freedom House indicator of the observance of civil liberties.11 For income inequality we interpolated and extended as necessary the Gini coefficients assembled
10 Alternative thresholds for the second-largest group, such as 10%, make no difference in the results.
11 Freedom House codes countries annually from 1972 on a seven-point scale based on a "checklist" that awards points for government observance of a long list of civil liberties and rule of law, including freedom of the press, religion, and association, independent j udiciary, equal treatment under the law, civilian control of police, "protection from political terror," secure property rights, and equality of opportunity. "Freedom from war and insurgency" is one element of their checklist, so we are careful to lag this independent variable. For Polity IV, we use the difference between the 11-point democracy and autocracy scales. Following the Polity coders' suggestions, we interpolate values for "transition period" years (—88), treat foreign occupation years (—66) as missing, and treat "interruptions" (—77) as zeros. See http://www.bsos.umd.edu/cidcm/polity/.
by Deininger and Squire (1996); using the country-average of Gini values produced the same results. For policies on religion, we coded, by decade, indicators for whether the state had an official religion, gave resources to one religion not available to others, regulated missionary activities, required religious groups to get official approval for religious activities, or singled out for or permitted harassment of a particular religious group. For policies on language, we coded by year whether a language spoken by at least 5% of the population received no official recognition at any level of government.12
One might argue, contrary to H\ above, that we should expect an association between measures of ethnic diversity and the occurence of ethnic strife, but not between ethnic diversity and civil war more broadly. In the limit this argument borders on tautology, since it would not be surprising if ethnic wars are rare in countries whose citizens think of themselves as ethnically homogeneous. However, one might ask if "ethnic wars" become more likely as ethnic diversity increases among those countries that have at least one nontrivial ethnic minority.
Hj: Among countries with an ethnic minority comprising at least 5% of the population, greater ethnic diversity should associate with a higher risk of ethnic civil war.
The measurement problem here is to say what an "ethnic" civil war is, and we suspect that under any plausible statement of the concept there will be numerous cases that are mixed or ambiguous. We coded as "ethnic" conflicts in which the fighters were mobilized primarily along ethnic lines, marking off 58 (51%) as ethnic, 20 (18%) as mixed or ambiguous, and 36 (32%) as not ethnic (excluding the anticolonial conflicts).
INSURGENCY
If many post-1945 civil wars have been "ethnic" or "nationalist" as these terms are usually understood, then even more have been fought as insurgencies. Insurgency is a technology of military conflict characterized by small, lightly armed bands practicing guerrilla warfare from rural base areas. To explain why some countries have experienced civil wars in this period one needs to understand the conditions that favor insurgency, which are largely independent of cultural differences between groups and even group grievances. These conditions are best summarized by way of a brief statement of the logic of insurgency.13
The fundamental fact about insurgency is that insurgents are weak relative to the governments they are
"Official recognition" implies use by some public, officially sanctioned entity. For language we relied mainly on Asher 1994 and Gunnemark 1992; and for religion, the U.S. State Department's 1999 Annual Report on Religious Freedom.
13 Though our formulations differ, we have been influenced here by Stathis Kalyvas's work on the Greek civil war. The literature on guerrilla warfare is extensive; see, for examples, Desai and Eckstein 1990, Griffith 1961, and Laqueur 1976.
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fighting, at least at the start of operations. If government forces knew who the rebels were and how to find them, they would be fairly easily destroyed or captured. This is true even in states whose military and police capacities are low. The total number of active rebels in many wars in which thousands of civilians have been killed (through the actions of both governments and rebels) is often in the hundreds or low thousands.
The numerical weakness of the insurgents implies that, to survive, the rebels must be able to hide from government forces. Several hypotheses follow.
Hg: The presence of (a) rough terrain, poorly served by roads, at a distance from the centers of state power, should favor insurgency and civil war. So should the availability of (b) foreign, cross-border sanctuaries and (c) a local population that can be induced not to denounce the insurgents to government agents.
Much scholarly writing holds that ethnic or class solidarity and grievances are necessary for Hgc, the local population's support of active rebels. In line with Kriger (1992) and some analysts of communist insurgencies (e.g., Clutterbuck 1967, Leites and Wolf 1970, and Thompson 1966), we argue that while grievances and ethnic solidarity can be helpful in this regard, they are not necessary. Instead, the key to inducing the local population not to denounce the active rebels is local knowledge, or information about who is doing what at the village level. Local knowledge allows the active rebels to threaten retribution for denunciation credibly.14 Ethnic insurgents use this informational advantage to great effect, often threatening and inflicting unimaginably harsh sanctions on "their own" people (Kalyvas 1999; Kriger 1992). The presence of an ethnic insurgency does not imply that the members of the ethnic group are of one mind in their determination to fight the state till they realize a nationalist dream. The immediate concern is how to survive in between government forces using violence to gain information or punish alleged rebel supporters and rebel forces using violence to punish alleged informants, "moderates," or government sympathizers.
An empirical implication of the importance of local knowledge is hypothesis Hg^' Having a rural base should greatly favor insurgency. In the city, anonymous denunciation is easier to get away with, giving the government an advantage in its counterinsurgent efforts.
Given the basic constraints posed by numerical weakness—the need to hide and not be denounced— various factors determine insurgents' ability to wage war. To survive, rebels need arms and materiel, money to buy them, or smugglable goods to trade for them. They need a supply of recruits to the insurgent way of
A "second-order" mechanism by which ethnicity may favor insurgency is that ethnic minorities are sometimes marked by dense social networks that are isolated from dominant group networks, thus giving an informational advantage to local rebels (Fearon and Laitin 1996). But such an advantage does not require ethnic distinctiveness.
life, and they may also need information and instruction in the practical details of running an insurgency.15
Most important for the prospects of a nascent insurgency, however, are the government's police and military capabilities and the reach of government institutions into rural areas. Insurgents are better able to survive and prosper if the government and military they oppose are relatively weak—badly financed, organizationally inept, corrupt, politically divided, and poorly informed about goings-on at the local level.
Effective counterinsurgency requires government forces to distinguish active rebels from noncombatants without destroying the lives and living conditions of the latter. This is an extremely difficult political, military, and organizational problem even for well-equipped and well-paid modern militaries; witness the U.S. military's failures in Vietnam (Avant 1994; Krepinevich 1986), early British efforts in Northern Ireland (Kennedy-Pipe 1997), or Soviet efforts in Afghanistan. For less well-financed and bureaucratically competent states, the problem appears to be nearly insoluble. Such states either cannot prevent the abuse of local powers by field commanders or may even permit these abuses as a sort of tax farming to the military. That is, they "pay" the soldiers with the opportunity to loot and pillage, a practice that tends to sustain rather than end insurgencies (see Keen 1998 for examples). Thus, we have the following hypothesis.
Hg: Proxies for the relative weakness or strength of the insurgents—their odds of being killed or captured for a given level of counterinsurgent effort by the government—should be associated with the likelihood that a country develops a civil war. In particular, a higher per capita income should be associated with a lower risk of civil war onset because
(a) it is a proxy for a state's overall financial, administrative, police, and military capabilities, and
(b) it will mark more developed countries with terrain more "disciplined" by roads and rural society more penetrated by central administration.
There is an additional reason why a lower per capita income should favor the technology of insurgency: (c) Recruiting young men to the life of a guerrilla is easier when the economic alternatives are worse. Though we try below, it is difficult to find measures to distinguish among these three mechanisms associating a low per capita income with civil war onset. We believe that the strong results for per capita income reported below are due largely to its acting as a proxy for state military and police strength relative to potential insurgents (a and b in H<)). The fact that measures such as the percentage of young males and male secondary schooling rates predict less well than per capita income is consistent with this conjecture, though not definitive.
In the case literature one frequently finds either that rebels leaders have spent time at guerrilla training camps in, for example, Libya, Afghanistan, Lebanon, or Mozambique (in the 1970s) or that they gained guerrilla experience in one insurgency that they apply in pursuing another.
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Additional factors that would be expected to affect (or proxy) the strength of an insurgent band relative to a state follow.
Hie,: The political and military technology of insurgency will be favored, and thus civil war made more likely, when potential rebels face or have available the following.
(a) A newly independent state, which suddenly loses the coercive backing of the former imperial power and whose military capabilities are new and untested (Fearon 1998).
(b) Political instability at the center, which may indicate disorganization and weakness and thus an opportunity for a separatist or center-seeking rebellion.
(c) A regime that mixes democratic with autocratic features, as this is likely to indicate political contestation among competing forces and, in consequence, state incapacity. (In contrast, pure autocracy tends to reflect the successful monopolization of state coercive and administrative power by an individual or group.)
(d) A large country population, which makes it necessary for the center to multiply layers of agents to keep tabs on who is doing what at the local level and, also, increases the number of potential recruits to an insurgency for a given level of income.
(e) A territorial base separated from the state's center by water or distance—for example, East Pakistan (now Bangladesh) from West Pakistan or Angola from Portugal.
(f) Foreign governments or diasporas willing to supply weapons, money, or training.
(g) Land that supports the production of high-value, low-weight goods such as coca, opium, diamonds, and other contraband, which can be used to finance an insurgency.
(h) A state whose revenues derive primarily from oil exports. Oil producers tend to have weaker state apparatuses than one would expect given their level of income because the rulers have less need for a socially intrusive and elaborate bureaucratic system to raise revenues—a political "Dutch disease" (Chaudhry 1989; Karl 1997; Wantchekon 2000). At the same time, oil revenues raise the value of the "prize" of controlling state power.
Partially excepting f, none of these conditions crucially involves cultural differences, ethnic minority status, or group grievances. We do not claim that these factors provide no help to would-be insurgents in specific cases. But, to reiterate, grievances and ethnic differences are too common to help distinguish the countries and years that see civil wars, and in any event the technology of insurgency does not require strong
popular grievances or ethnic solidarities to operate effectively. The latter point suggests a contrast to FLi-Fk.
H\\: After controlling for per capita income (or other measures of state strength), neither political democracy, the presence of civil liberties, higher income inequality, nor nondiscriminatory linguistic or religious policies should associate strongly with lower odds of civil war. Given the right environmental conditions, insurgencies can thrive on the basis of small numbers of rebels without strong, widespread, popular support rooted in grievances and, hence, even in democracies.
As for measures, for "rough terrain" we use the proportion of the country that is "mountainous" according to the codings of geographer A. J. Gerard.16 This does not pick up other sorts of rough terrain that can be favorable to guerrillas such as swamps and jungle, and it takes no account of population distributions or food availability in relation to mountains; but it is the best we have been able to do for Hga. For we use Penn World Tables and World Bank data on per capita income, estimating missing values using data on per capita energy consumption.17 For H\qa (new states) we mark countries in their first and second years of independence; for i?ioh (political instability) we use a dummy variable indicating whether the country had a three-or-greater change on the Polity IV regime index in any of the three years prior to the country-year in question.18 For countries that mix democratic and autocratic features (called "anocracies" or "semidemocracies" in the international relations literature and "praetorian regimes" by Huntington 1968) we mark regimes that score between —5 and 5 on the difference between Polity IV's democracy and autocracy measures (the difference ranges from —10 to 10). Country population (i?iod) is based largely on World Bank figures. For oil exporters we marked country-years in which fuel exports exceeded one-third of export revenues, using World Bank data.19 We coded a dummy variable for states with noncontiguous territory ourselves (i?ioe)-20
Gerard produced this measure for the DECRG project on civil wars at the World Bank. Our sample of countries differs slightly, so we estimated values for 21 missing countries using the difference between the highest and the lowest point of elevation in each country, which is well correlated with the mountains measure (0.78 in logs).
17 We used income growth rates from the World Development Indicators 2001 to extend the estimates in the Penn World Tables 5.6 and then used the per capita energy consumption estimates provided by the COW project to estimate additional missing values. For details see Fearon and Laitin 2003.
18 For this variable, "transition periods" and "interruptions" (which indicate a "complete collapse of central authority") are coded as instability; foreign occupations are treated as missing.
19 The data are for five-year intervals beginning in 1960; we interpolated for years after 1960, set the value to that in 1960 for years prior to 1960, and used country-specific sources for a few countries without World Bank coverage.
20 Countries with territory holding at least 10,000 people and separated from the land area containing the capital city either by land or by 100 km of water were coded as "noncontiguous." Ignoring the colonial empires, 25 of our 161 countries meet this criterion at some time since 1945.
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The remaining hypotheses (H^-H^, Hw and Hiog) present more difficult measurement challenges. Whether availability of a rural base favors civil war (Hgd) is better tested in a research design where ethnic groups are the unit of analysis, so that groups with different geographic concentrations can be compared.21
Although it is possible to code rebellions in progress for whether the rebels receive shelter and support from foreign countries (Hgb, Hot), the potential availability of these aids to rebel strength is difficult to observe prior to the onset of fighting. In two special cases, the potential availability of support from a foreign power to governments is observable—in Soviet policy (the "Brezhnev doctrine") in Eastern Europe and French policy with regard to its former colonies in subSaharan Africa.22 We would expect such support to increase the relative advantage of government forces against potential insurgents and thus associate with lower rates of civil war onset. We also consider a more tenuous measure of potential support to rebels—the number of civil wars ongoing in neighboring countries—which might yield more easily available weapons, training, or the presence of experienced guerrillas.23
EMPIRICAL ANALYSIS
Our central hypotheses concern the relationship between ethnic and religious diversity or structure, on the one hand, and the susceptibility of a country to civil war, on the other. Several multivariate analyses of the country-year data are presented below, but the main story emerging from them is made clear by the contour plot in Figure 2.
Are More Diverse Countries Prone to Civil War?
Figure 2 shows how probabilities of civil war onset vary at different percentiles for country income (on the x axis, measured in lagged 1985 dollars) and ethnic homogeneity (on the y axis, measured by the population share of the largest ethnic group). The lines in the plot show the probability of war onset in the next five years for a country at the given level of income and ethnic homogeneity. For example, countries at the twentieth percentile in terms of the size of their largest ethnic group—thus quite ethnically diverse—but at the eightieth percentile on income have had about a 5%
21 Using the Phase III Minorities at Risk (MAR) data, Fearon and Laitin (1999) found that groups without a rural base area were far less likely to be engaged in violent conflict with the state, even after controlling for various country- and group-specific factors. Toft (1996) was the first to note and examine the strong bivariate relationship in the MAR data.
22 U.S. support to rightist regimes in Latin America during the Cold War might also qualify, although this was perhaps more offset by support for armed insurgency in this area from the Soviet Union and Cuba.
23 The presence of valuable minerals or the suitability of land for the cultivation of narcotics is also codable in principle, but at present we lack such measures (-f/ioe)- Nor do we have measures for the comparative disadvantage of governments in access to village-level information (Hgc).
chance of civil war outbreak in the next five years. In contrast, countries at the eightieth percentile on ethnic homogeneity and at the twentieth percentile on income had a 15% chance of war in the next five years.24
Note that for any level of ethnic diversity, as one moves up the income scale (to the right in Figure 2), the odds of civil war decrease, by substantial factors in all cases and dramatically among the most homogeneous countries. The richest fifth is practically immune regardless of ethnic composition. In contrast, for given levels of country income, no consistent effect is associated with variation in ethnic homogeneity (i.e., moving up or down the figure). Among the poorest countries where we observe the highest rates of civil war, the data indicate a tendency for more homogeneous countries to be more civil war-prone. Among the richest countries there may be a weak tendency for the most homogeneous countries to have fewer civil wars, but the size of the effect, if any, is small.
The empirical pattern is thus inconsistent with H\, the common expectation that ethnic diversity is a major and direct cause of civil violence. Nor is there strong evidence in favor of H, which expects ethnic strife to be activated as modernization advances. Ethnic diversity could still cause civil war indirectly, if it causes a low per capita income (Easterly and Levine 1997) or a weak state. But then the mechanisms that actually produce the violence would more likely be those of the insurgency perspective than the culturalist arguments in either perennialist or modernist forms.
The data for Figure 2 omit the anticolonial wars, and the analysis does not control for other possible influences on civil strife enumerated earlier. We consider these issues next.
Multivariate Results
We coded a variable onset as "1" for all country-years in which a civil war started and "0" for all others.25 Model 1 in Table 1 shows the results of a logit analysis using onset as the dependent variable and a fairly full specification of independent variables discussed above. Prior war is a control variable indexing whether the
24 The figure was produced using R's locfit package, with a smoothing parameter of 0.9, and transforming annual probabilities of outbreak to five-year equivalents. The figure looks highly similar if we use other measures of ethnic diversity, such as fractionalization.
25 We do not code as ones years in which a civil war continues, which would be relevant if our focus were causes of war duration rather than onset. Nor do we drop country-years that have an ongoing war (as in Collier and Hoeffler 2001), since this would omit the 14 wars in our data that start while another war is in progress. Other approaches to the dependent variable and estimation—such as making the dependent variable "1" for all war years and using dynamic probit or Poisson models that interact independent variables with a lagged dependent variable (Jackman 2001; Przeworski et al. 2001)— produce virtually identical results. Only one country-year in the data has more than one onset (Soviet Union 1946, with one Ukrainian and three Baltic rebellions). We treat this as a one in the analyses reported here, though there are no significant changes if we use Poisson regression instead (treating the dependent variable as a count) or weight this observation four times in the logit likelihood. Using "rare events logit" (King and Zeng 2001) had no appreciable impact on any estimates reported.
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FIGURE 2.  Probability of Civil War Onset per Five-Year Period
GDP/capita in lagged 1985 U.S. dollars 48 808 1433 2724 5689 17280
0 20 40 60 80 99
Percentile
country had a distinct civil war ongoing in the previous year.26
Per Capita Income. Per capita income (measured as thousands of 1985 U.S. dollars and lagged one year) is strongly significant in both a statistical and a substantive sense: $1,000 less in per capita income is associated with 41 % greater annual odds of civil war onset, on average. Holding other variables at their median values, a country in the tenth percentile on income has an 18 % chance of a civil war outbreak over a decade, compared to an 11% chance for a country at the median income and a 1% chance for a country at the ninetieth percentile ($573, $1,995, and $9,505, respectively). The income variable is not just a proxy for "the West," whose states
With onset as the dependent variable, the data are grouped duration data and we need to consider the possibility of temporal dependence between observations. One approach is dynamic probit; see footnote 25. We also tried Beck et al.'s (1998) method of including dummies for each successive "peace year" prior to an onset, or fitting natural cubic splines. This had no appreciable effect on the estimates, and the splines were jointly insignificant.
might have low rates of civil war for reasons of culture or history that have little to do with income. The estimated coefficient drops only to —0.28 when a dummy for the West is included and remains strongly significant despite the high correlation between the two variables. The relationship holds even within the poorest regions. Among the (mainly) former colonies of Africa, the Middle East, and Asia, we estimate that $1,000 less in income corresponds to 34% greater annual odds of outbreak.27
Ethnic and Religious Composition. The estimates for the effect of ethnic and religious fractionalization are substantively and statistically insignificant. Alternative measures of ethnic and religious diversity—such as the
27 Contrary to Hibbs 1973 and Hegre et al. 2001, adding the square of per capita income does not significantly improve the fit of the model. Regarding Hi, the interaction of income and ELF has the expected sign but is not significant. For lack of space, we report the details of these and other "nonresults" mentioned below in the tables included in Fearon and Laitin 2003.
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TABLE 1.  Log it Analyses	of Determinants of Civil War		Onset, 1945-99		
			Model		
				(4)	(5)
	(1)	(2)	(3)	Civil War	Civil War
	Civil War	"Ethnic" War	Civil War	(Plus Empires)	(COW)
Prior war	-0.954**	-0.849*	-0.916**	-0.688**	-0.551
	(0.314)	(0.388)	(0.312)	(0.264)	(0.374)
Per capita income3b	-0.344***	-0.379***	-0.318***	-0.305***	-0.309***
	(0.072)	(0.100)	(0.071)	(0.063)	(0.079)
log(population)3b	0.263***	0.389***	0.272***	0.267***	0.223**
	(0.073)	(0.110)	(0.074)	(0.069)	(0.079)
log(% mountainous)	0.219**	0.120	0.199*	0.192*	0.418***
	(0.085)	(0.106)	(0.085)	(0.082)	(0.103)
Noncontiguous state	0.443	0.481	0.426	0.798**	-0.171
	(0.274)	(0.398)	(0.272)	(0.241)	(0.328)
Oil exporter	0.858**	0.809*	0.751**	0.548*	1 269***
	(0.279)	(0.352)	(0.278)	(0.262)	(0.297)
New state	1 yog***	1.777***	1.658***	1.523***	1.147**
	(0.339)	(0.415)	(0.342)	(0.332)	(0.413)
Instability3	0.618**	0.385	0.513*	0.548*	0.584*
	(0.235)	(0.316)	(0.242)	(0.225)	(0.268)
Democracy30	0.021	0.013			
	(0.017)	(0.022)			
Ethnic fractionalization	0.166	0.146	0.164	0.490	-0.119
	(0.373)	(0.584)	(0.368)	(0.345)	(0.396)
Religious fractional ization	0.285	1.533*	0.326		1.176*
	(0.509)	(0.724)	(0.506)		(0.563)
Anocracy3			0.521*		0.597*
			(0.237)		(0.261)
Democracy301			0.127		0.219
			(0.304)		(0.354)
Constant	-6.731***	-8.450***	-7.019***	-6.801***	-7.503***
	(0.736)	(1.092)	(0.751)	(0.681)	(0.854)
N	6327	5186	6327	6360	5378
Note: The dependent variable is coded "1" for country years in which a			Divil war began and "0'	in all others. Standard errors are in	
parentheses. Estimations performed using Stata 7.0.		*p< .05; **p< .01;	**p< .001.		
3 Lagged one year.					
bln 1000's.					
c Polity IV; varies from -10 to 10.					
d Dichotomous.					
proportion of the largest group and the log of the number of languages spoken by at least 1%—prove to be just as unrelated. The ethnic diversity measures show a strong bivariate relationship with civil war onset (not so for the religion measures), but this evaporates when we control for income.28
Nor are countries that are ethnically or religiously polarized in the sense of H3 more likely to experience major civil violence. When we add dummy variables for countries that have an ethnic or religious majority and a minority of at least 8% of the country's population, both are incorrectly signed and neither comes close to statistical significance. This finding does not depend on which other variables are included in the model.
Ethnic War. The strong effect of per capita income remains even when we restrict attention to "ethnic wars,"
28 Collier and Hoeffler (2001) find the interaction of ethnic and religious fractionalization to be negatively related to onset. Others find that fractionalization has a nonmonotonic relation to conflict. Neither relationship appears in these data; we suspect that one reason may be listwise deletion on missing economic data in other data sets.
while evidence of an independent effect of cultural diversity is surprisingly weak. In Model 2 (Table 1), the dependent variable marks the onset of wars that we coded as "ethnic" or partially "ethnic," and we consider only countries with at least a 5% ethnic minority. The coefficient for ethnic fractionalization barely changes. The same is true for our other measures of ethnic diversity. Our two measures for religious diversity give weak and inconsistent results, and support for H-j diminishes further if we code the "partially" or "ambiguously" ethnic wars as nonethnic. 9
Democracy and Civil Liberties. Broad social and political grievances should be lower, on average, in political democracies. But contrary to H4 and consistent with Hu, civil war onsets are no less frequent in democracies after controlling for income, as shown by the positive and statistically insignificant coefficient for democracy,
29 Coefficients for political instability and mountains diminish in this subsample, partly because the associations appear to have been weaker for ethnic wars and partly due to the omission of highly homogeneous countries.
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the (lagged) Polity IV measure. The results are the same if we use Przeworski et al.'s dichotomous measure instead (available for 1950-91) or the lag of Freedom House's measure of observance of civil liberties (available for 1972-99). In the former case the sign is "wrong," while in the latter the sign is consistent with h4 but the coefficient on civil liberties is thoroughly insignificant.
Some past studies of civil strife found an "inverted-U" relationship with democracy and sought to explain this by the observation that the most autocratic regimes can repress dissent and thus avoid civil violence despite facing the highest levels of popular grievance (Hegre et al. 2001; Muller and Weede 1990). This observation does not explain why the leaders of a partially democratic regime are not able to implement full autocracy or democracy to avoid conflict and opposition. As suggested in Hide we suspect that the answer is often that "anocracies" are weak regimes, lacking the resources to be successful autocrats or containing an unstable mix of political forces that makes them unable to move to crush nascent rebel groups. Consistent with this hypothesis and with the prior studies, Model 3 (Table 1) shows that a dummy variable marking anocracies takes a positive coefficient. In substantive terms the estimate suggests that these regimes have about 68% greater odds of civil war outbreak in any given year than would a full autocracy. This is so despite the fact that we are controlling for recent political instability, which is much more common in anocracies.30
Linguistic and Religious Discrimination. Added to Model 3, our measures of state discrimination against regional languages or against minority religions are not associated with systematically higher risks of civil war onset.31 This nonresult persists when we restrict the sample to those countries with at least a 5% religious or ethnic minority.
Inequality. Whether in a bivariate model or added to Model 3, the Gini coefficient estimates of income inequality do not come close to either statistical or substantive significance. The poor quality of the inequality data, available for only 108 countries, does not allow us to go beyond the claim that there appears to be no powerful cross-national relationship between inequality and onset, consistent with H\\.
30 In Model 3 Democracy is a dichotomous variable marking regimes that scored higher than 5 on the Polity scale; the excluded category is autocracies. For Model 3 we followed Polity IV's suggestion in coding regime "interruptions" as anocracies; if these values are instead interpolated, the resulting anocracy indicator gets a smaller estimated coefficient that is not quite significant at the 5 % level, while that for political instability increases. Another issue, raised by Hegre et al. (2001), is that the observation of some violence may lead Polity IV to code democracies as less "democratic" and autocracies as less autocratic (since there is mobilized opposition). So if there is low-level violence preceding the reaching of our thresholds, some of the effect of "anocracy" may be that it is picking up nascent civil war.
31 We tried the several religion indicators both separately and as a single measure based on a factor analysis of the components. Discrimination against regional languages is in fact associated with slightly lower odds of civil war onset, consistent with Laitin 2000.
New States and Political Instability. Consistent with i^ioa, the odds of civil war onset are estimated as 5.25 times greater in the first two years of a state's independent existence than in other years, a huge effect (Model 3). For the "median country," this translates to an 11 % chance in its first two years. Political instability at the center matters in other years as well. The odds of onset in a given year are estimated to increase by 67% if there was instability in governing arrangements in any of the previous three years.32
Mountains and Noncontiguous Territory. Mountainous terrain is significantly related to higher rates of civil war. A country that is about half "mountainous" (ninetieth percentile) and otherwise at the median has an estimated 13.2% chance of civil war over the course of a decade. A similar country that is not mountainous at all (tenth percentile) has a 6.5% risk. The estimated sign for states with noncontiguous territory is consistent with i?ioe, but its 95% confidence interval includes the possibility of no effect.33
Population. Holding other variables at medians, the estimated risk of civil war over the course of a decade for a country at the tenth percentile in population is 6.4%, versus 16.4% for a country at the ninetieth percentile (1.4 versus 56.3 million, e.g., Botswana versus Iran). This effect is not due to large states being more ethnically diverse. We are controlling for ethnic diversity, and in any event it turns out that there is essentially no correlation between diversity measures and log of size, even if we omit the relatively homogeneous China.34
Oil, Islam, Young Males. Consistent with i?ioh, deriving at least one-third of export revenues from fossil fuels is estimated to more than double a country's odds. Based on Model 3, the "median country" had a 10% chance of civil war over a decade, whereas the same country as an oil exporter would have an estimated 21% chance.
Oil producers are disproportionately Middle Eastern, which raises the question of whether this variable might proxy some other relevant attribute of these countries. But a dummy for the North Africa/ Middle East region is insignificant when added to Model 3, while the estimate for oil is barely affected. Huntington (1996) argues that "Islam has bloody borders" and "bloody innards" because Islamic societies have cultural and demographic features that make them violence-prone. When we add a variable
32 Snyder (2000) argues that democratization puts states at greater risk for civil war, ethnic in particular. Coding variables for three-or-greater moves toward and away from democracy on the Polity index, we find in these data that moves away from democracy are much more strongly associated with civil war onset in the next year than moves toward it, though both forms of instability elevate the risk. Hegre et al. (2001) found the same thing using COW civil war data.
33 Dropping this or other "insignificant" variables from Model 3 barely affects the remaining estimated coefficients.
34 Huntington (1996) argues that rapid population growth puts states at greater risk for civil war. Using the average growth rate for the three prior years, we find no significant impact.
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measuring the percentage of Muslims in each country to our main specification,35 it takes a positive sign but is not statistically significant. The effect of oil remains strong.
Huntington also argues that societies with a surfeit of young males will be prone to civil violence, suggesting this as a part of the explanation for Islam's "bloody innards." Given that young males have physical and perhaps psychological characteristics that make them apt guerrillas, our arguments on insurgency point in the same general direction. If we include a lagged measure of the proportion of males aged 15 to 24 in the population in Model 3, it has the expected positive sign,36 but the estimate is highly uncertain (p — .21); one problem is that percentage of young males has a strong negative correlation with income, and income gets the better of it when both are included. The same is true for male secondary schooling rates (cf. Collier and Hoeffler 2001).
Foreign Support. One determinant of the prospects for insurgency is the availability of third-party support to either the rebels or the government of the state in question. "Availability" is difficult to observe ex ante, however. A possible proxy is the number of civil wars ongoing in neighboring countries in the previous year, which might increase the availability of arms, support, and seasoned guerrillas. Adding the lagged version of this variable to Model 3, its sign is as predicted, but it is not significant (p — .33). Civil war next door is too common, occuring in 44% of the country-years in the sample.
Another possible proxy is foreign support to governments against domestic challengers. A dummy variable for "Soviet bloc" prior to 1991 cannot be included in the logit analysis because it perfectly predicts peace. But by itself this observation is consistent with our argument.37
In the late 1980s, Mitterand's government departed from long-standing French foreign policy by supporting, to a limited extent, democratization in some of its former sub-Saharan colonies. This involved encouraging "national conferences," elections, and some political opposition, which all suggested that the prior policy of immediate military support for French-speaking dictators might have changed. Civil war rates for former French African colonies had been much lower than those for other sub-Saharan states. The 25 others saw 17 civil war onsets before 1990, a rate of 2.4 per 100 country-years. The 16 former French colonies had only three onsets in the same period, for a rate of 0.65 per 100 country-years (Chad in 1965, Senegal [Casamance] in 1989, and Mali in 1989). If a variable marking former French colonies in sub-Saharan Africa prior to 1990 is included in Model 3, its estimated coefficient is —1.0, which implies an almost-threefold reduction in the annual odds of civil war onset (p — .11;
Coded from the CIA Factbook and a variety of country-specific sources.
36 Data from the World Bank, linearly interpolated for missing years within countries.
37 Foreign support may be at least as important as communist party structure in explaining Huntington's (1968) observation that the communist countries rarely faced insurrections.
the other estimates remain stable). A dummy variable for all former French colonies is unrelated to civil war onset, which suggests that the observed effect in sub-Saharan Africa is due to the mechanism behind Hicn rather than the effects of French colonial administration or law.
Other Variables and Robustness Checks
Anticolonial Wars. Figure 2 and the multivariate analyses above omitted the 13 anticolonial wars in five colonial empires (Britain, France, Belgium, Portugal, and The Netherlands). Including them is problematic for both theoretical and empirical reasons, but so is ignoring them. The main practical obstacle is the lack of comparable data. However, by using the ethnic fractionalization, population, mountainousness, and income data for each colony in its first year of independence, we were able to produce annual estimates of these variables for each empire. The income estimates are systematically too high—we use, for example, Nigerian GDP per capita in 1962 as an estimate of its income as a British colony in 1945. This creates some bias against the income variable and in favor of the ELF, which has a median value of 0.83 for the 114 "empire years," compared to 0.34 for nonempire years.
Model 4 reports a logit analysis parallel to our specification in Model 1 (Table 1), omitting only the democracy variable and religious fractionalization (which is hard to estimate for the empires due to shared religions between colonies and metropoles). Given that the empires were quite civil war-prone and highly diverse, it is not surprising that the estimated coefficient for ELF increases. Surprisingly, though, it remains statistically indistinguishable from zero, while, excepting nonconti-guity, the others change little. Noncontiguous states are now estimated to have had 2.2 times the odds of civil war in this period, other things being equal. Because the empires are all noncontiguous and because noncontigu-ity otherwise does a better job than the ELF at picking out civil wars onsets, it is given greater substantive and statistical significance by the logit. If we drop noncon-tiguity, the estimate for ELF increases to 0.62—which corresponds to a 59% increase in risk moving from the tenth to the ninetieth percentile—but still fails statistical significance at the 5% level (p— .07). Thus even if we include the anticolonial wars, the evidence that ethnic diversity directly causes states to be more civil war prone remains slim at best.38
Stepping back from the statistical analysis, we observe that these five imperial states managed their empires for many years before World War II with fairly little active rebellion despite the same levels of ethnic fractionalization, noncontiguity, and mountainousness. Nor did discrimination and oppression suddenly increase in the empires after the war, causing
We created a democracy estimate for the empires by taking a weighted average of the metropole's lagged Polity democracy score and —10, weighting by the metropole's proportion of total imperial population. Adding this or dummies for "anocracy" and democracy to Model 5 has no substantive impact.
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anticolonial movements as a response. Rather, the war greatly weakened the main imperial states materially, and the new international legal order (the U.N. system) gave support to anticolonial movements. These shocks to the relative power of the metropoles help explain "civil war onset" in these cases (Fearon 2001).
Regional Effects. Different regions of the world share a variety of historical, cultural, and economic traits. It is reasonable to wonder if any of the variables considered in the multivariate analysis just proxy for such factors. Further, if regional dummy variables do not add to the model's explanatory power, then we have managed to account for the influence of regional characteristics with our more general independent variables. We find that if we add all (but one) regional dummies to Model 3, the coefficients and significance levels for our other variables are little affected. A likelihood-ratio test fails to reject the null hypothesis that "regions do not matter" beyond the included variables (p — .22). Including region dummies individually reveals that none has a rate of civil war onset significantly different from what one would expect on the basis of the country characteristics already included in the model.
Period and Fixed Effects. If added to Model 3, dummy variables marking each decade (but one) are jointly significant in a likelihood-ratio test (p — .04), showing evidence of a general upward trend in civil war risk after the 1940s. Adding a dummy for the 1940s and a variable marking the year indicates that from 1950 the odds of civil war outbreak rose about 2% per year, controlling for the other variables. As noted earlier, there is no secular trend when we do not control for other factors. Part of the explanation is that the median of country incomes roughly doubled from 1950 to 1999, which "should have"—based on Model 3—reduced the onset odds for the "median country" by about 35%. The fact that the rate of outbreak remains fairly constant while incomes generally increased in effect penalizes income in Model 3. When year is added, the effect estimate for income increases to —0.36 (the other effect estimates stay steady, except for noncontiguity, which becomes statistically significant at p — .035). We do not know what accounts for steady rates of outbreak despite increasing incomes. Increased international inequality (so that there is a set of persistently poor countries at risk for civil war), greater availability of small arms, and diffusion of insurgency "know-how" come to mind, but are just conjectures.
This observation also raises the question of how much the estimated impact of income is due to crosscountry comparisons and how much to increasing income within given countries associating with civil peace. Applying conditional fixed effects logit to Model 3 without the variables that have little or no temporal variation (mountains, noncontiguity, ethnic and religious fractionalization) and with a control for year, we find that the estimated coefficient for income drops only to —0.24 but is no longer significant {p — .16). Using log of income, however, returns the same co-
efficient that log of income takes in the standard logit on the full sample (—0.78), significant at p— .02.39 In addition, the effect estimates for the other variables are, with one exception, virtually identical to the estimates in the full, "pooled" model, the significance remaining high for all but anocracy and oil (which has little temporal variation). The exception is population, which varies vastly more across countries than within them over time. While bigger countries are more civil war-prone, there is no evidence that population growth within a country raises the risk.
Primary Commodity Exports. Using an "expanded" version of the COW data, Collier and Ffoeffier (2001) find that the risk of civil war onset is maximized when primary commodity exports comprise about 32 % of the country's GDP, with risk declining on either side of this figure. They propose that, up to a point, higher levels of primary commodity exports provide more motivation and opportunity for rebels to support themselves through "looting." Beyond this point, the revenue gains available to the state are said to be large enough to make civil war less likely.
We find little evidence of such a relationship in our data. Neither the share of primary commodity exports in GDP nor its square is remotely significant when added to Model 3*
We agree with the general argument behind Collier and Hoeffler's hypothesis. In our terms, insurgency should be more feasible if sources of financing are readily available. But we doubt that primary commodity exports are a good measure of financing potential for rebels. This measure combines oil, agricultural products, and metals and minerals, which, except for some minerals, are hard to exploit without control of a national distribution system and ports. Oil exports may be relevant not so much because they finance rebel groups but, as we argued, because they mark relative state weakness at a given level of income.41 A better measure for financing potential would focus on the presence of minerals or contraband that can reward control of a small enclave with huge profits (Leonard and Strauss 2001).
Trade Openness. Using a measure of "state failure" that includes both civil war and "disruptive regime transitions," Esty et al. (1998) found that trade share of GDP strongly predicted civil peace. Using the Penn World Tables measure of trade as a share of the GDP, we find no such relationship in our data. Trade is related to civil peace in a bivariate logit, but this is because smaller countries have more trade and less civil war.
39 Whether we use income or logged income in the standard logit makes for no significant differences.
40 The data series on primary commodity exports begins in 1960 and is available only at five-year intervals. We interpolated missing values and extended the 1995 values through 1999. We also tried Collier and Hoeffler's procedure of grouping the data by five-year periods beginning in 1960, again finding no relationship.
41 Our oil variable is moderately correlated with the primary commodities measure, at r = .46, but the latter and its square remain insignificant when oil is dropped from the model.
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Alternative Definitions and Coding for "Civil War."
Our coding rules admit civil conflicts in which at least 1,000 have been killed. Some might argue that this threshold is too low to distinguish properly between "civil war" and, say, terrorism. When we recode the 30 conflicts in our sample estimated to have killed fewer than 5,000 as zeros, the results for Model 3 are nearly identical.42
We also checked to see how our results differed if we based the coding of civil war onset on the lists given by Collier and Hoeffler (2001), the COW project, and Doyle and Sambanis (2000). As shown in Model 5 (Table 1), which bases onset on the COW data (1945-92), the coefficients and significance levels for the "insurgency" variables are remarkably stable.43 We obtain quite similar results for the other two coding schemes. Although these four civil war lists differ on many specific start years and, to some extent, on what cases constitute "civil wars" at all, there proves to be substantial shared variation. For example, 53 of the 93 COW civil wars in the sample start in the same year as an onset in our data, and 68 start within two years of one of our onsets. At the country level, the bivariate correlation between our estimate of the total number of wars by country and the equivalent for the others ranges from 0.71 with Collier and Hoeffler to 0.82 with Doyle and Sambanis.
CONCLUSION
The prevalence of internal war in the 1990s is mainly the result of an accumulation of protracted conflicts since the 1950s rather than a sudden change associated with a new, post-Cold War international system. Decolonization from the 1940s through the 1970s gave birth to a large number of financially, bureaucratically, and militarily weak states. These states have been at risk for civil violence for the whole period, almost entirely in the form of insurgency, or rural guerrilla warfare. Insurgency is a mode of military practice that can be harnessed to various political agendas, be it communism in Southeast Asia and Latin America, Islamic fundamentalism in Afghanistan, Algeria, or Kashmir, right-wing "reaction" in Nicaragua, or ethnic nationalism in a great many states. The conditions that favor insurgency—in particular, state weakness marked by poverty, a large population, and instability—are better predictors of which countries are at risk for civil war than are indicators of ethnic and religious diversity or measures of grievances such as economic inequality, lack of democracy or civil liberties, or state discrimination against minority religions or languages.
42 The coefficient on income increases 21%, noncontiguity becomes significant, and anocracy weakens slightly. We coded total deaths ourselves, based on Brogan 1998, Institute for International and Strategic Studies 2000, Sivard 1996, Valentino 2002, and country-specific sources.
43 The one exception is religious fractionalization, which just manages significance at the 5% level here. This does not occur in the other data sets, and even with the COW data the estimate for religious fractionalization is highly sensitive to which other variables are included in the model.
How could democracy and cultural or religious homogeneity fail to associate with civil peace across countries? Viewing "ethnic wars" as a species of insurgency may help explain this paradoxical result. If, under the right environmental conditions, just 500 to 2,000 active guerrillas can make for a long-running, destructive internal war, then the average level of grievance in a group may not matter that much. What matters is whether active rebels can hide from government forces and whether economic opportunities are so poor that the life of a rebel is attractive to 500 or 2,000 young men. Grievance may favor rebellion by leading nonac-tive rebels to help in hiding the active rebels. But all the guerrillas really need is superior local knowledge, which enables them to threaten reprisal for denunciation.
If our analysis is correct, then policy makers should not assume that civil wars and the "failed states" they sometimes produce are temporary phenomena of the immediate post-Cold War world. Nor should policy makers or academics infer that ethnic diversity is the root cause of civil conflict when they observe insurgents in a poor country who mobilize fighters along ethnic lines. Instead, the civil wars of the period have structural roots, in the combination of a simple, robust military technology and decolonization, which created an international system numerically dominated by fragile states with limited administrative control of their peripheries.
Regarding policy implications, the spread of democracy and tolerance for ethnic and religious minorities should be major foreign policy goals because they are desirable for their own sake, but not with the expectation that they are "magic bullets" for the prevention or resolution of civil war. Sometimes recommended as a general international policy for resolving ethnic civil wars (e.g., Kaufmann 1996), ethnic partitions should be viewed as having large international implications and high costs. International support for partition would increase the expected benefits for rebels, who, we have argued, may be able to get a nasty civil war going on the basis of small numbers when the conditions for insurgency are right.
Policies to redress grievances, or, in the limit, partition, could be important to resolve ongoing conflicts. We cannot say on the basis of this research, which focused on civil war onset rather than termination. We find little evidence that civil war is predicted by large cultural divisions or broadly held grievances. But it seems quite clear that intense grievances are produced by civil war—indeed, this is often a central objective of rebel strategy. These could well pose obstacles to settlement.
Regarding prevention, our analysis suggests that while economic growth may correlate with fewer civil wars, the causal mechanism is more likely a well-financed and administratively competent government. In specific terms, international and nongovernmental organizations should develop programs that improve legal accountability within developing world militaries and police, and make aid to governments fighting civil wars conditional on the state observing
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counterinsurgency practices that do not help rebels recruit militias. Governments that follow horrible, war-perpetuating counterinsurgency practices or are so corrupt as to be hopeless should be left on their own or, when there are major implications for regional stability or international terrorism, be viewed as candidates for "neotrusteeship" under the United Nations or regional military and political organizations such as NATO and the European Union. The latter system, which we already see operating, in effect, in Bosnia, Kosovo, and East Timor, should be rationalized so as to improve internal coordination among the many players involved in such operations.
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