Human Rights Violations and Violent Internal Conflict

Abstract

This research project uses econometric methods and comparative, cross-national data to see whether violations of human rights increase the likelihood of the onset or escalation of violent protest, terrorism and/or civil war. The findings show that these types of violent internal conflict will occur and escalate if governments: (1) torture, politically imprison, kill, or “disappear” people, (2) do not allow women to participate fully in the political system, including allowing them to hold high level national political office, and (3) do not allow women to participate fully in the economic life of the nation by ensuring equal pay for equal work, by encouraging their entry to the highest paid occupations, and by protecting them from sexual harassment at their workplaces. These types of violations of human rights and the existence of large horizontal inequalities in societies independently produce an increased risk of the onset and escalation of many forms of violent internal conflict. The results also provide some evidence for the argument that there is a trade-off between liberty and security.

1. Introduction

In the 2011 World Development Report, Robert Zoellick, then President of the World Bank, noted that “civil conflict costs the average developing country roughly 30 years of GDP growth, and countries in protracted crisis can fall over 20 percentage points behind in overcoming poverty” (p. xii). He wrote that, “Finding effective ways to help societies escape new outbursts or repeated cycles of violence is critical for global security and global development.”

Subsequently, the World Bank and UN Development Program began a joint study to examine how development and other policies contribute or could contribute to the prevention of violent conflict. The final report (United Nations and World Bank 2018) provided recommendations to governments and development organizations on preventing violent conflicts. An earlier version of this paper was commissioned by the UN and World Bank for their potential use in making those final recommendations.

Specifically, the authors of this paper were asked to explore the potential for a human rights-based approach to reducing the likelihood and intensity of violent internal conflicts around the world. In other words, how much variation in various forms of internal conflict could be explained mainly by the human rights practices of governments. We were asked to limit the consideration of other explanations of internal political violence to essential control variables and various forms of inequality.

The underlying argument explaining why violations of human rights and high levels of inequality would both lead to more internal political violence is grievance theory. In brief, grievance theory can be traced back to the work of Gurr (1968) who noted that government policies that imposed hardships on citizens could create frustration, which could lead to aggression. Grievance theory as an explanation of internal political violence has been neglected relative to other theoretical arguments in large part due to the way that grievances have been measured and conceptualized in the conflict literatures (Blattman and Miguel 2010).

In this paper, we review the empirical studies that test hypotheses about internal political violence drawn from grievance theory, develop new hypotheses, and test those hypotheses. We contribute to existing research findings by examining the effects of a broad range of human rights violations as potential explanations of conflict. We also show the effects of these potential drivers of conflict on three types of internal conflict.

Previous research on the relationship between human rights and conflict mostly examined one type of human rights and one type of conflict. Therefore, the main advantage of our approach is its breadth. The literature suggests that the explanations for violent protest, terrorism, and civil war are different. We ask whether human rights violations matter at all in each case. Our strong findings warrant more careful examination controlling for potential alternative explanations that we have not considered. Some results are consistent with the findings of previous research. Others suggest new avenues of potentially fruitful investigation.

Some of the rights examined here such as freedom of speech and press and freedom of assembly and association have received little or no attention in previous studies explaining internal political violence. They are directly relevant to the current policy debate over whether there is a trade-off between liberty and security. The results provide some evidence that the trade-off is real.

We find that several types of violations of human rights and the existence of large horizontal inequalities in societies independently produce an increased risk of the onset and escalation of many forms of violent internal conflict. Previous research shows that horizontal inequality alone makes the onset of violent internal conflict more likely (Cederman et al. 2013). However, this is the first study to test whether both horizontal inequality and violations of human rights each have an independent effect as drivers of internal conflict, even when controlling for the effects of the other.

This research project was also designed to introduce scholars and policymakers to the two most commonly used human rights data projects—the CIRI+CIRIGHTS and the Political Terror Scale projects. In the next section, we explain the types of human rights that these projects measure and how both projects quantify the human rights practices of governments.

2. Defining and Measuring Human Rights

Human rights are the basic rights that every individual is entitled to as a member of the human race. The United Nations has played the leading role in establishing international human rights law but has not developed quantitative measures of the extent to which its members respect, protect or fulfill those entitlements. The term “human rights” represents a broad concept that includes numerous specific types or kinds of rights. We choose, however, to limit our attention to three categories of rights: (1) physical integrity rights (protections from extrajudicial killing, disappearance, torture, and arbitrary/political detention), (2) women’s rights and (3) civil and political liberties (e.g., freedom of speech and press).

The UN framework of human rights responsibilities for states stipulates that they have the obligation to respect, protect, and fulfill the rights included in international treaties. The obligation to respect means that states must refrain from interfering with or curtailing the enjoyment of human rights. The obligation to protect requires states to protect individuals against human rights abuses committed by agents of the state (e.g., police, soldiers or prison guards), private actors and/or corporate entities. Finally, the obligation to fulfill means that states must take positive action to facilitate the enjoyment of basic human rights. Thus, state action or inaction can violate human rights.1

Beginning in the early 1980s, scholars began to construct the first cross-national measures of state violations of citizens’ most basic human rights—physical integrity rights. The Political Terror Scale (PTS), the CIRI data project (Cingranelli and Richards 2010; Cingranelli et al. 2014), and the CIRI+CIRIGHTS (Cingranelli et al. 2018) data sets contain the most widely used and cited of the indices measuring state violations of these entitlements. The CIRIGHTS dataset updates the CIRI scores for the years 2012–2015 using the CIRI methodology. Both the combined CIRI+CIRIGHTS and the PTS data projects provide ordinal measures of levels of physical integrity rights violations for more than 190 countries going back to 1976 (PTS) and 1981 (CIRI+CIRIGHTS). Both indices are based on the coding of information contained in two annual human rights reports: the U.S. Department of State Country Reports on Human Rights Practices and the Amnesty International Annual Report. Using the CIRI+CIRIGHTS data set, the physical integrity rights index can be disaggregated into extrajudicial killing, disappearances, torture, and political imprisonment.

Human rights information and scores based on available annual reports are not perfect. For one thing, states oftentimes hide (or attempt to hide) nefarious activities. Moreover, witnesses might be killed or imprisoned, or silenced through intimidation. Thus, accurate measures of violations are rare, and all counts contain an inherent amount of measurement error. Even when violations are catalogued, specificity is almost always limited. Seldom, if ever, would a State Department or Amnesty Report say that a country had carried out X number of cases of torture, or had in detention Y number of political prisoners. Because of the lack of precision in the annual reports, the PTS and the CIRI+CIRIGHTS indices both employ ordinal measures—“more or less”—when compared to other states. In that way, adjectives are important—the difference between “widespread” as opposed to “frequent,” or “common” as opposed to “reports of”—in determining a country’s assigned score.

There are many other sources of information about the human rights practices of national governments including state self-reporting. Most states report on the extent to which they are meeting their treaty obligations and, since 2008, the human rights practices of most states have been evaluated in reports produced by the UN periodic review process.

The PTS (Wood and Gibney 2010) and CIRI+CIRIGHTS projects do not use these other sources of information. Their scores rely exclusively on evaluations included in the annual reports produced by Amnesty International and the US State Department because they are the only reports that have been produced for a long time (since 1976) for all member states of the United Nations. Using different source materials for different countries would inhibit cross-national comparisons, since every source of information has its own biases. Introducing new sources of information about all countries but only for recent years would make it harder to compare the human rights performance of particular national governments over time.

Notwithstanding these limitations, the CIRI+CIRIGHTS and PTS data allow for the exploration of a number of important political issues. Most essentially: in which countries are physical integrity rights violated—and where are they not? Are there certain patterns of state behavior and have these changed over time? Do certain forms of government or regimes protect human rights better than do others? Have certain specific policies such as trade liberalization and bilateral foreign aid had an effect on a state’s human rights practices? In the present analysis, the PTS and CIRI+CIRIGHTS data are used to explore the relationship between levels of physical integrity violations and civil conflict.

3. Three Types of Violent Internal Conflict

Internal political violence can take many different forms. Lynchings, public executions, gang rape, looting, bar or street brawls, coups, violent demonstrations, terrorism, and war all fall under the broad category of interpersonal violence (Tilly 2003). In this paper, we are primarily interested in exploring violent internal conflict where the use of violence has a political goal, makes some demand of the state/is directed at the state, and is carried out collectively. Most human interactions occur without violence. War, whether between states or within states is rare as are violent demonstrations, riots and terrorism. Yet, when these events do occur, they cause significant death, damage, and destruction and have the potential to spark cycles of violence. One of the most consistent findings in the conflict literature is that the best predictor of violent conflict today is violent conflict in the past. Cycles of conflict once started are hard to break.

This paper uses a grievance framework to explain why people engage in collective violence. We argue the violation of human rights creates grievances that make violence more likely. We choose three types of collective violence that have received the majority of attention in the contentious politics literatures: violent protests and riots, terrorist attacks, and civil war. Civil war is commonly used as an indicator of the existence of violent internal conflict. But violent protests and domestic terrorism are more commonly experienced types of internal conflict. So, besides civil war, we analyze the extent to which violations of human rights help us understand the onset and escalation of these other types of conflict events.

We conceptualize violent protests as events in which groups of people gather together in a public place within a state and use violence to press their demands for state action. We look at the number of violent protests occurring within each state within each year. These events exclude political rallies, strikes which make no demand of the state, conflict between citizens or civil society groups, and armed resistance to the state (such as rebellion or terrorism). They include riots and strikes that turn violent as long as individuals make a demand of the state. Violence can range from destruction of property to shooting at police or the military. When citizens destroy property and/or use violence against state agents, this often signals significant grievances. This behavior is illegal and represents a threat to state power. Violent protests can cripple the economy, result in the death of citizens and state agents, and have the potential to escalate into civil war or overthrow the regime (Bell et al. 2013). We make no distinction between whether violence was the result of a strategic decision, an emotional response to grievances and injustice, or a response to state tactics.

Domestic terrorism is distinct from other forms of intense internal conflict. We conceptualize terror attacks as those whose aim is not to weaken the state’s coercive capacity but aims to influence the wider audience who witness such attacks (Bakker et al. 2016). This is distinct from civil conflict and violent protest in which dissidents directly confront the state. This is also distinct from nonviolent dissent aimed at pressuring the state through economic, political or other means without the use of violence (Chenoweth and Cunningham 2013). Terror attacks are a strategy used by groups to achieve a political goal (Pape 2003). We focus on domestic rather than international terrorism, because domestic terrorism is more likely to result from grievances within the domestic population. We elaborate on this point in the next section.

A civil war is a high intensity conflict between organized groups within the same state or country. Most civil wars involve regular armed forces of the state as one of the parties to the conflict. The aim of non-governmental actors may be to take control of the country or a region, to achieve independence for a region, or to change government policies. Civil wars are usually identified by the number of battle deaths that occur within a given year, and depending on the threshold one uses, between one-third and one-half of countries in the world have experienced a civil war (Blattman and Miguel 2010). Civil war causes destruction, loss of life, and impedes development often on a much larger scale than violent protest or terrorism.

These three types of violence—violent protest, terrorism, and civil war—have often been treated separately. That is, studies have looked at a single type of violence to explain its onset, duration, or end using a variety of explanations. The factors that explain one form of violence may be different from those that explain another (Scarritt and McMillan 1995; Regan and Norton 2005). However, the commonality between these is the use of violence collectively towards some political end.

We argue that violations of human rights can help us explain why we see collective violence and can explain multiple forms of violent internal conflict. Yet there is little work comparing how human rights violations differ in their effect on various forms of violent conflict. There is also little work explaining why we sometimes see a rapid shift from one tactic to another (Tilly 2003). When do violent protests escalate into terror attacks or rebellion? For example, Syria experienced widespread violent protests calling for the removal of President Bashar Hafez al-Assad before the country broke out into civil war. Violent protest also occurred in Tunisia in 2010 sparking the Arab Spring and the overthrow of former President Zine El Abidine Ben Ali, although it was absent in the years prior to 2010. By exploring violent protest and whether it escalates, we may be able to predict where we are likely to see civil war and terrorism. Indeed, our argument suggests that if the state responds to protests with repression, this escalation is more likely.

We see these three forms of conflict as alternative, sometimes substitutable strategies for those who are aggrieved. Violent protest has lower coordination costs than terrorism which in turn has lower coordination costs than civil war. We thus assume that citizens are likely to turn to lower cost forms of violence before they escalate to higher cost forms of violence. In this way we see violent protest as preceding terrorism which precedes civil war.

Of course, we recognize that this is not always the case. A rebel group may turn to terror tactics when its chances of victory start waning. Similarly, we may not see protest at all in countries where the cost of protest is very high. Civil war or terrorist attacks sometimes break out in the absence of previous violent protests. Still, we believe that not taking into account what other forms of collective dissent existed in the immediate past is likely to bias our understanding of what causes violent conflict (see Harbom and Wallensteen 2009). Thus, we explain these three forms of violence using the violation of human rights as well as other forms of collective dissent that happened in the immediate past.

4. Theory

The literature has established that both greed and grievance play a role in explaining why people take violent actions against their government (Bell et al. 2013; Gurr 1968; Tilly 2003; Rassler 1996; Oliver and Myers 2002). Greed and grievance refer to the two main arguments put forward by scholars who study civil war and other forms of political violence directed against the state such as terrorism (Collier and Hoeffler 2002). The “greed” or “opportunity” argument is that individuals rebel when they stand to gain something from it. People initiate violence against the state or join a violent group based on an informal cost-benefit analysis in which they compare joining a rebellion with not joining.

“Grievance” stands for the argument that people rebel when they are angry with their governments. Violence is undertaken to remedy or express dissatisfaction with a perceived injustice or inequality in society rather than to gain material benefit. In practice, scholars have long recognized that both play an important role in understanding conflict and that it is difficult to untangle and isolate which motivation drives conflict (Blattman and Miguel 2010). Our theoretical argument about human rights violations encompasses elements of both theoretical arguments.

As noted above, we conceptualize state violations of human rights as an important source of grievances against the state. We assume that people want their governments to respect all internationally recognized human rights. When a government violates some of those rights, people are harmed. As a result of being harmed, they have a desire to better their situation. We also assume that people value government respect for some types of human rights more than others. Thus, the desire to use violence against the state is greater when some rights are violated rather than others.

Intensity of violation also matters. Greater violation of rights highly valued by the people is more likely to stimulate a violent response than lesser violation. To us, this seems to be more about grievance or frustration as Gurr conceptualized it than it is about greed. However, in Gurr’s own work explaining civil war, he emphasized that rebellion would not occur if potential combatants would have little chance of succeeding.

It is difficult to authoritatively determine the causal connection between repression and rebellion, and there is much debate about this in the literature (Ritter and Conrad 2016). Young (2013) highlights the interdependence among repression, dissent, and violence. He argues that states that repress their citizens are most likely to face dissident challenges, which in turn increases the incumbent regime’s incentives to violently repress challengers and increases the risk of civil war. A cause must precede its effect, and it is often impossible to establish the precise sequence of repression, dissent, and political violence using the country year as the unit of analysis (Walsh and Piazza 2010). This is partly because government repression and some combination of violent protest, domestic terrorism, and civil war may all occur in a particular country in one year.

Violations of human rights are one source of grievances, and higher levels of horizontal inequality is another, independent source of grievances. Horizontal inequalities are economic inequalities among groups of people within societies, where the members of each group share a common identity determined by their shared social, political, religious, or cultural characteristics. Horizontal inequality differs from vertical inequality in that the latter is a measure of inequality among individuals, while the former is a measure of inequality among groups.

A relatively high level of horizontal inequality within society is mainly produced by institutionalized discrimination favoring the members of some groups. Over time, this systematic discrimination is likely to lead to greater economic disparities between privileged and other groups. Another way to think about it is that the existence of institutionalized discrimination results in the creation of reinforcing cleavages. Reinforcing cleavages exist, for example, when the members of one ethnic group have significantly fewer resources and political power than members in another ethnic group. In a system like that, systems of oppression, domination or discrimination reinforce one another.

As noted, horizontal inequality is unjust (Stewart and Langer 2008). There may be an argument for moderate levels of vertical inequality to create incentives for hard work. But there is no reason why some people should be better off simply because of such characteristics as their ethnicity, religion or gender. The victims of systematic oppression are likely to blame their government for the discrimination against them, and, under some circumstances, this dissatisfaction among the members of the out groups will lead to rebellion (Cederman et al. 2013).

5. Hypotheses

5.1. More Respect for Physical Integrity Rights, More Peace

The literature has examined the relationship between government repression and popular dissent, where repression is defined as actions taken by the government which raise the costs of disagreeing with the regime in power (Tilly 2003; Moore 2000; Carey 2006). Typically, the concept of repression refers to all forms of human rights violations perpetrated by the state or agents of the state. According to the bulk of this research, in the long-term government repression of human rights causes an increase in the scope and intensity of grievances held by a population, leading to the onset and escalation of internal conflict (Gurr and Moore 1997; Carey 2006).

Within the human rights and conflict literature, most of the focus has been on the degree, as opposed to the type, of government repression (Gurr and Moore 1997). For example, Regan and Norton (2005) found that a higher level of violations of physical integrity rights by the state was associated with a higher probability of civil war. They used an index of violation of physical integrity rights as their causal variable. Goodwin (2001) concludes that state repression creates the belief among the population that there is “no other way out” besides armed revolt against an unjust and abusive regime.

Previous studies have also found that high levels of violations of physical integrity rights by government forces are counterproductive during periods of ongoing internal violence. Thoms and Ron (2007), for instance, conclude that violations of physical integrity rights by state actors are associated with the escalation of existing political conflicts. Moreover, indiscriminate state violence against civilian populations generates grievances and pushes civilians into the arms of opposition actors, thereby exacerbating political conflict and feeding the rebellion (Mason and Krane 1989; Kalyvas and Kocher 2007).

Other related studies have also noted a strong relationship between state repression and the risk of terrorism in the state. Specifically, as state actors engage in higher levels of violent coercion and physical repression against the population, the risk of terrorist violence directed against the state and its population increases steeply (Bakker et al. 2016; Piaaza 2017), while increasing respect for these rights reduces the risk of terrorism (Walsh and Piazza 2010). Thus, we posit our first hypothesis:

H1. 

The more a government violates personal security rights, the greater the risk of the onset and escalation of all forms of internal conflict.

But, within the category of physical integrity rights, which violations are likely to produce the most violence? There are important differences among the four physical integrity rights in terms of how “extreme” and how “visible” each type is to the citizenry. The use of extrajudicial killing and disappearance would be most closely related to subsequent political violence by citizens if extreme forms of coercion generate the most intense grievances against the government. If the desire for political violence is stimulated the most when governments use the most visible forms of physical integrity violations, then we would expect to find that political imprisonment would be most closely related to subsequent political violence by citizens.

Globally, governments use extrajudicial killing and disappearance the least. In this sense, these forms of violation of physical integrity rights are the most extreme forms. In contrast, torture is, by far, the most commonly used form of government repression among the types of physical integrity violations examined here. Political imprisonment was common during the Cold War, but became more rare after the wave of democratization that followed (Cingranelli and Richards 2010).

Political prisoners are widely publicized by human rights INGOs like Amnesty International. Thus, political imprisonment is the form of repression most visible to citizens and its visibility is increasing as internet access increases. Torture is also widely publicized by INGOs, but it is harder for INGOs to detect, because torture is generally practiced out of view of the general public while victims are in police or military custody. Making citizens disappear and killing them without a trial are government actions that are, by comparison, more easily hidden from the citizenry.

The four physical integrity rights also vary in terms of how likely it is that citizens will blame violations on politicians rather than rogue state agents. A recent study (Bell et al. 2013) found that there was more political violence when governments frequently imprisoned citizens for political reasons or made them “disappear”. The authors argued that these coercive techniques may create more citizen dissatisfaction (grievance) than other types of violations of physical integrity rights, because citizens perceive political imprisonment and disappearances as the direct result of the deliberate policy choices of politicians. Other types of physical integrity violations may result mostly from the inability of politicians to control the behavior of police, prison guards, and soldiers.

Similarly, Walsh and Piazza (2010), who studied domestic terrorism, also found higher levels of terrorism in countries whose governments imprisoned citizens for political reasons and made them disappear. They also found higher levels of terrorism in countries that committed extrajudicial killings. Based on the overlapping findings of these two studies, we hypothesize that:

H2. 

Higher levels of political imprisonment and disappearances are more likely to increase the risk of the onset and escalation of internal conflict.

5.2. More Respect for Women’s Rights, More Peace

Numerous studies note the influence of gender equality, women’s social status, and respect for women’s rights on the likelihood or severity of various forms of political violence. For instance, recent studies suggest that improvements in societal gender equality or “women’s rights” reduces the level of violence employed during interstate conflicts (Caprioli 2000; Mlambo-Ngcuka 2018), decreases the likelihood that a state experiences a violent internal conflict (Caprioli 2005; Melander 2005a), reduces the likelihood that a state experiences terrorism (Harris and Milton 2016), and reduces the severity and frequency of physical integrity violations perpetrated by the state (Melander 2005b). Greater respect for women’s rights has also been linked to an increase in the likelihood that peacekeeping operations are more successful at ensuring long-term stability (Gizelis 2009, 2011).

Other previous studies specifically link women’s access to political authority and policy making to the risk of violent conflict. There is some evidence that greater female representation in national legislative assemblies reduces the risk of internal conflict (Melander 2005b) or international conflict (Koch and Fulton 2011). In addition, increasing women’s representation to the levers of political power in the aftermath of civil war has been shown to increase the durability of post-conflict peace and reduce the risk of conflict relapse (Demeritt et al. 2014; Tripp 2016; Shair-Rosenfield and Wood 2017). Thus, broadly speaking, the existing literature on this topic largely suggests that improvements in women’s rights reduce the likelihood that the state will engage in or experience violent conflict.

There are a number of arguments about why repression of women’s rights leads to greater violence against the state. Most of them rest on some variation of grievance theory. For example, Murdie and Peksen (2015, p. 182) argue that when a government does not respect women’s economic or political rights, it is likely that the capabilities of a woman in that nation greatly differ from her expectations, either with a reference category of the male counterparts in the country or with a reference category of what women outside of her country are receiving. Thus, she is more likely to have grievances consistent with relative deprivation theory (Gurr 1968).

Caprioli (2005) agrees with this argument. However, she goes further by contending that greater political and economic discrimination by males against females in a society is an indication of a greater willingness by the state to use domination against most, if not all, subordinate groups. From this perspective, low respect for women’s rights is a proxy for low respect for minority rights of all kinds. Similarly, Hudson et al. (2009) find that higher levels of women’s physical security—which they view as reflective of core gender norms and violent patriarchy—are predictive of the overall peacefulness of a state. While the theoretical reasons vary, the empirical expectation is clear and previous findings have been consistent:

H3. 

As government respect for women’s political and economic rights in a state decreases, the risk of the onset and escalation of all forms of internal conflict increases.

5.3. More Respect for Civil and Political Liberties, More Internal Political Violence

The critical and widely accepted assumption underlying ongoing scholarly debates and recently instituted governmental policies is that reducing protections on civil liberties such as the right to privacy increases national security from terrorism and other forms of violence directed against the state (Dragu 2011). For example, Bell et al. (2013) argued that more political violence was likely in states that respected civil liberties, thereby allowing dissatisfied citizens to coordinate their anti-government activities. Their findings showed that political violence was higher if governments respected their citizens’ right to freedom of assembly and association. Other civil and political liberties may also allow anti-government views to be expressed and may make it easier for dissidents to mobilize. For example, respect for Freedom of speech and press allows citizens to express and to aggregate their grievances. Freedom of domestic movement allows dissatisfied individuals to travel to meet with one another. Thus, we hypothesize that:

H4. 

If a government respects civil and political liberties, then the risk of the onset and escalation of all forms of internal conflict also increases.

6. Inequality and Systematic Discrimination

While numerous previous studies have focused on vertical or individual level inequalities within a state (e.g., the Gini index), we follow Cederman et al. (2013) and focus specifically on horizontal inequalities, which, as noted above, are inequalities in economic, social or political dimensions or cultural status between ethnic, racial, or religious groups.

Empirical evidence of the effect of identity patterns on conflict is somewhat inconclusive, but Sambanis (2001); Ellingsen (2000) and Reynal-Querol (2002) demonstrate that identity patterns are associated with civil unrest, and Collier and Hoeffler (2002) demonstrate that it is the dominance of one ethnic group that puts states most at risk of civil war. Others tend to find a lack of support for the influence of ethno-linguistic patterns on conflict.

Additionally, we hypothesize that the risk of conflict escalation increases as the size of the population that faces discrimination or exclusion from core political and economic power grows. In part, our argument here rests on the assumption that systematic repression—often of a high magnitude—by the incumbent regime is necessary to sustain the exclusion of specific groups from political and economic processes, particularly where that excluded group constitutes a substantial portion of the population. In other words, we assert that exclusion is sustained only by high levels of coercive violence against the excluded group, and as the size of this population grows, the likelihood increases that its members resort to violence in response to state repression.

H5. 

As horizontal inequality increases, the risk of the onset and escalation of all forms of internal conflict also increases.

H6. 

As the size of the group that suffers from systematic discrimination and exclusion grows, the risk of the onset and escalation of all forms of internal conflict also increases.

7. Research Design

In our quantitative analyses, we consider how changes in various types of human rights practices and the degree/type of inequality in a society contribute to the onset and escalation (or de-escalation) of three types of internal conflict. Our analyses are based on samples of nearly 150 nation states during the periods 1990–2005 and 1990–2015.2 We first describe the relevant variables we include in our empirical analyses and then discuss the specific empirical modeling technique that we employ.

7.1. Dependent Variables

We explore three different types of internal violence: violent anti-government protests, domestic terrorism, and civil war. The first measure is a count of the number of violent anti-government protests (Clark and Regan 2016). The second measure of violence is the number of domestic terrorist attacks (START 2016). The final measure is the number of civil war battle deaths (Melander et al. 2016).

We operationalize violent anti-government protests as a count of the number of violent protests in a country year. These are protests or riots by 50 or more individuals within the state who make demands of their government. These protests turned violent and resulted in the destruction of private property, clashes with police, or injury to state agents at the hands of protesters. This data cannot tell us whether violence was a strategic decision, an emotional response, or a response to the behavior of police activity. These data were taken from Clark and Regan (2016).

We operationalize terrorism as the number of domestic terror attacks in a country year. Civil war is conceptualized as the number of civil conflict deaths in a country year, with 25 deaths being the lower bound. Our measures are taken from the Uppsala Conflict Data Program’s—Battle Related Deaths Dataset (Melander et al. 2016). We use the number of battle deaths as an imperfect proxy for the number of civil war events. Civil war deaths are imperfect here because they are quite different than the other two dependent variables which are events data, but are distributed in a way that look much like the other two (a large number of zeros and over-dispersion). However, we were unable to obtain civil war event data that would serve our purposes and so make the assumption that a larger number of civil war deaths is associated with a larger number of civil war conflict events.

These three types of violence differ. Studies examining violent protest have often been separated from those involving terrorism or civil war. Few studies to date have explored more than one type of internal violence in the context of human rights in a single study (see, for example, Abouharb and Cingranelli 2008; Bell et al. 2013). However, we conceptualize the decision to use one type of violence (protest, terror attacks, rebellion) as part of a similar and inter-related set of processes. When citizens are unable to address their grievances with lower cost strategies (such as elections or non-violent collective action), they may turn to higher cost forms of violent dissent. Similarly, the organizational costs of these strategies differ; violent protest is less costly than organizing a terror attack which in turn is less costly than mounting a rebellion.

We model the relationships between these three types of violence as though there was a process of escalation. Non-violent protest is used to predict violent protest. Non-violent and violent protest are used to predict terror attacks. Finally, non-violent, violent, and terror attacks are used to predict civil war. We recognize that there are other forms of violence we might include and other ways of modeling the relationships between these forms of violence. However, we choose this strategy because it allows us to control for alternative forms of dissent that may be ongoing and alter decisions to engage in one type of violence over another, as well as the probability that lower levels of violence predict higher levels of violence. We assume that a country that faces a large number of non-violent protests is more likely to experience violent protest in the following year. We assume that if a country experiences non-violent or violent protests, it is more likely to experience terrorism or civil war in the following year. Finally, we assume that if a country experiences non-violent protest, violent protest, or terror attacks in the previous year it is more likely to experience civil war in the following year. Although imperfect, this attempts to address how citizens decide between these three different violent strategies which is rarely addressed in the empirical literature.

7.2. Independent Predictors of Interest

Our main independent variables measure government respect for various human rights. Physical integrity rights (torture, disappearances, extrajudicial killings, and political imprisonment) are captured by two different measures: the Political Terror Scale (Gibney et al. 2016), an ordinal scale ranging from 0 to 5, and the Physical Integrity Index, an ordinal scale with ranges from 0 to 8, from the CIRI Human Rights Data Project and updated by the CIRIGHTS Data Project using the CIRI methodology. We invert the Political Terror Scale so that higher values indicate greater respect for physical integrity rights on both scales. The source material for both the CIRIGHTS data and the Political Terror Scale come from the annual US Department of State Country Reports on Human Rights Practices as well as the annual Amnesty International report.

In our second model, we use the disaggregated components of the Physical Integrity Index: torture, disappearances, extrajudicial killings, and political imprisonment. Each of these is ordinal and coded from 0 (widespread violations) to 2 (no violations). We also include another measure of human rights: women’s rights. Women’s rights is an additive scale of women’s economic and women’s political rights from the CIRI and CIRIGHTS Human Rights Data Projects. Women’s rights captures both discrimination and inequality as it relates to women in society, and can also serve as a proxy for societal inequality against other subordinate groups in society. Where women’s rights are not respected, it is unlikely that other subordinate groups enjoy human rights protections.

We explore whether inequality has an independent effect on conflict once we account for levels of human rights protection. Inequality is captured in four separate measures: the size of the largest discriminated group, negative horizontal inequality, positive horizontal inequality and vertical inequality. The first three measures are taken from Buhaug et al. (2014). Size of the largest discriminated group indicates the percentage of a country’s population that is made up of the largest discriminated group. Negative horizontal inequality is the country GDP per capita divided by the mean GDP per capita of the poorest group in society. Positive horizontal inequality is the mean GDP per capita of the richest group divided by the country GDP per capita. For both of the horizontal inequality measures, a larger number indicates a greater level of inequality. Vertical inequality is taken from the Standardized World Income Inequality Database and is a GINI coefficient with higher levels indicating greater inequality of disposable income in a country (Solt 2016).

In our final model, we include a number of civil and political rights each taken from the CIRI and CIRIGHTS database and coded as ordinal measures ranging from 0 (widespread violations) to 2 (no violations). We include freedom of assembly and association, freedom of speech, freedom of domestic movement, and freedom of international movement. A more detailed explanation of all CIRIGHTS variables can be found in the Appendix A.

7.3. Control Variables

We include some control variables to rule out some common confounders that are known to influence both conflict and human rights. Given the number of dependent variables and the number of human rights we are exploring we are unable to control for all of the individual factors taken from various conflict and human rights literatures which may explain both our conflict variables and our human rights variables. Instead we opt to control for some of the most common confounders and include a lagged dependent variable to help absorb the statistical consequences of any additional confounders which are missing. Given the number of variables we are exploring as well as the number of models we opt for a more parsimonious modeling strategy and ask future researchers to explore some of these relationship in more depth, especially how these rights are inter-related. For our control variables we include population size, economic development and state capacity measured as GDP per capita, and GDP growth taken from the World Bank World Development Indicators (World Bank 2016). We also control for regime type using the −10- to 10-point ordinal scale taken from the Polity IV dataset (Marshall et al. 2016). We opt to exclude the polity measure from our final model as civil and political rights are highly correlated with measures of democracy.

Table A1. Variables and Sources.

Dependent Variables	Indicator	Source
Violent protests	Number of violent anti-government protests	Mass Mobilization dataset
Terrorist attacks	Number of domestic terrorist attacks, the year 1993 is missing	Global Terrorism Database
Civil war deaths	Number of civil war battle deaths	Uppsala Conflict Data Program—Battle Related Deaths
Independent Variables	Indicator	Source
Political Terror Scale (PTS)	Ordinal scale, 1 (terror has expanded to the whole population) 5 (secure rule of law, no political imprisonment, torture is rare, political murders are rare)	Political Terror Scale
Physical Integrity rights (CIRI)	Ordinal scale, 0 (torture, political imprisonment, extrajudicial killings, and disappearances are widespread) 8 (full respect for physical integrity rights)	CI-RIGHTS data project
Women’s rights	Women’s economic and political rights. Ordinal scale 0 (no respect) 6 (full respect)	CI-RIGHTS data project
Freedom of Assembly and Association	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Freedom of Speech	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Right to Self-Determination	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Freedom of Religion	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Judicial Independence	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Freedom of domestic Movement	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Freedom of International Movement	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Protest repression	Number of protests where police responded with repression (crowd control + beatings + killings + shootings)	Mass Mobilization dataset
Size of largest discriminated group	(Size of largest discriminated ethnic group)/(size of largest discriminated ethnic group + size of group(s) in power)	Buhaug et al. (2014)
Horizontal inequality	(Country GDP per capita)/(mean per capita income for poorest group)	Buhaug et al. (2014)
Vertical inequality	GINI index of net inequality	Standardized World Income Inequality Database
Control Variables	Indicator	Source
GDP per capita	Gross domestic product divided by country population	World Bank WDI
GDP growth	Yearly change in gross domestic product as a percentage	World Bank WDI
Democracy	Ranges from −10 (autocratic) to 10 (democratic)	Polity IV dataset
Population Size	Country population, logged	World Bank WDI
Dependent Variables	Indicator	Source
Violent protests	Number of violent anti-government protests	Mass Mobilization dataset
Terrorist attacks	Number of domestic terrorist attacks, the year 1993 is missing	Global Terrorism Database
Civil war deaths	Number of civil war battle deaths	Uppsala Conflict Data Program—Battle Related Deaths
Independent Variables	Indicator	Source
Political Terror Scale (PTS)	Ordinal scale, 1 (terror has expanded to the whole population) 5 (secure rule of law, no political imprisonment, torture is rare, political murders are rare)	Political Terror Scale
Physical Integrity rights (CIRI)	Ordinal scale, 0 (torture, political imprisonment, extrajudicial killings, and disappearances are widespread) 8 (full respect for physical integrity rights)	CI-RIGHTS data project
Women’s rights	Women’s economic and political rights. Ordinal scale 0 (no respect) 6 (full respect)	CI-RIGHTS data project
Freedom of Assembly and Association	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Freedom of Speech	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Right to Self-Determination	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Freedom of Religion	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Judicial Independence	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Freedom of domestic Movement	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Freedom of International Movement	Ordinal scale, 0 (no respect) 2 (full respect)	CI-RIGHTS data project
Protest repression	Number of protests where police responded with repression (crowd control + beatings + killings + shootings)	Mass Mobilization dataset
Size of largest discriminated group	(Size of largest discriminated ethnic group)/(size of largest discriminated ethnic group + size of group(s) in power)	Buhaug et al. (2014)
Horizontal inequality	(Country GDP per capita)/(mean per capita income for poorest group)	Buhaug et al. (2014)
Vertical inequality	GINI index of net inequality	Standardized World Income Inequality Database
Control Variables	Indicator	Source
GDP per capita	Gross domestic product divided by country population	World Bank WDI
GDP growth	Yearly change in gross domestic product as a percentage	World Bank WDI
Democracy	Ranges from −10 (autocratic) to 10 (democratic)	Polity IV dataset
Population Size	Country population, logged	World Bank WDI

in the Appendix A lists all indicators and data sources.

7.4. Empirical Strategy

As a first cut at examining the relationships between the independent and dependent variables discussed above, we present a series of simple difference-of-means tests comparing the rate of conflict events in repressive versus non-repressive countries as well as various descriptive statistics. We believe that these tests provide some face validity to our theoretical claims. We further believe that the use of simpler comparison of means tests helps increase the accessibility of empirical social science work.

For our primary tests of the hypotheses, we rely on zero-inflated negative binomial regression models. We select a zero-inflated negative binomial (ZINB) model because our dependent variables in all cases are event data that are likely both overdispersed and subject to contagion. In other words, variance in the counts of events are substantially greater than their means (overdispersion), and we expect that conflict events are not independent of one another (contagion). Additionally, there are large numbers of zeros in the dependent variables that may result from distinct processes that separate countries into two categories: those at a lower baseline risk of conflict and those with a higher baseline risk. The ZINB models use an inverse logit regression to account for structural zeroes in the sample (true zeroes) followed by a second stage negative binomial regression equation to account for the number of observed events, including the zeroes represented in the normal negative binomial distribution (sampling zeroes). Put differently, the model allows us to evaluate the baseline risk that a country experienced any level of a given type of conflict during the year as well as the frequency of each type of conflict event (severity). This model also allows us to test whether our independent variables of interest affect each of these differently.3

In all of our models we cluster standard errors by country because of the high likelihood that within the same country these errors are correlated over time, which may bias our estimates. We also include a lagged dependent variable in all models to account for autocorrelation and minimize the possibility of reverse causality or simultaneity.4 A lagged dependent variable also allows us to control for some of the confounders which may be missing from our model. An additional benefit of including a lagged dependent variable is that it allows us to model the change in the dependent variable between the previous period and the current, rather than simply the level of the dependent variable at a given time point. We also lag all independent variables to further address concerns about endogeneity and reverse causality.

Our model choice also allows us to minimize the chance of reverse causality or simultaneity. In maximum likelihood models, as long as our independent variables and our dependent variables are not predicted by the exact same set of predictors included in the model in the exact same way then we do not have to worry about these issues as we would need to in ordinary least square models (see Greene 2003, pp. 745–48; King 1998, sct. 8.2). We opt to exclude the control variables as well as measures of internal dissent from the tables in the main paper as these tables are already quite busy. The full models can be found in the Appendix A for those interested.5

In Section 8.1, we look at whether there is any face validity to the claim that countries with physical integrity rights violations experience higher levels of internal violence. In Section 8.2, we explore the relationship between physical integrity rights, inequality and our measures of conflict. In Section 8.3, we disaggregate physical integrity rights and add women’s rights. Finally, in Section 8.4, we add civil and political rights. Section 8.5 shows the results of the control variables and other forms of dissent. Section 8.6 has a summary of our findings.

8. Findings

8.1. Respect for Physical Integrity Rights and Violent Internal Conflict: Difference of Means

Our argument implies that countries with greater respect for physical integrity rights (torture, disappearance, political imprisonment and extrajudicial killing) are likely to experience less violent conflict. A simple way to test this is to see whether countries that respect physical integrity rights experience less violent conflict than their more repressive counterparts.

Table 1. Physical Integrity Rights and Conflict Events.

Respect for Physical Integrity Rights	Average Number of Violent Protests	Average Number of Terrorist Attacks	Average Number of Civil War Deaths
Low	1.05	48.85	440.37
High	0.66	10.25	63.16
T value	6.48 ***	8.51 ***	7.94 ***
Number of observations	4043	4017	5158

Note: “High” indicates a CIRI+CIRIGHTS Human Rights data project physical integrity rights index score of five or higher. Low indicates a score four or lower. Results are unchanged if we use the Political Terror Scale and separate countries into a high group, a score of four or five on the inverted scale, and low, a score of three or lower. *** indicate p < 0.001.

shows that countries that do respect human rights (i.e., respect for human rights is high) experience on average fewer conflict events (violent protests, terrorist attacks, and civil war deaths) than do countries with low human rights respect. Countries with high levels of respect for physical integrity rights experience 37% fewer violent protests, 79% fewer terrorist attacks, and 86% fewer civil war deaths on average. A t-test (difference of means) indicates that these differences are statistically significant at the 99.9% level.

Figure 1 (below) plots the average number of conflict events over time for states with high respect for physical integrity rights and those with low respect. The top left graph shows the number of violent protests in a year. On average, we see that repressive states have more violent protests than non-repressive states for all but one year. We see the same trend for the number of terrorist attacks though the difference is much more pronounced. The largest difference can be seen in the number of civil war deaths. For every year between 1990 and 2015, there are significantly more civil war deaths in repressive states than there are in non-repressive states. These figures once again show support for our hypothesis.

For all three figures, it is notable that in recent years the number of conflict events is increasing. Over the past 25 years, the number of violent protests, terrorist attacks, and civil war deaths were highest in 2015. Across the board, we see that countries that have better respect for human rights within their borders tend to have fewer conflict events. These results are the same regardless of which physical integrity rights measure we use

8.2. Respect for Physical Integrity Rights and Inequality: Zero-inflated Negative Binomial Model

Table 2. Respect for Physical Integrity Rights, Inequality and Internal Conflict.

Model 1 outcome equation (Equation (2))—zero-inflated negative binomial—1990–2005
	PTS	CIRI	PTS	CIRI	PTS	CIRI
	No. of Violent protest	No. of Violent protest	No. of Terrorist attacks	No. of Terrorist attack	No. of Civil war deaths	No. of Civil war deaths
Protest repression	−0.0474	−0.0469
	(0.0367)	(0.0351)
Political Terror Scale	0.0764		−0.363 ***		−0.342 ***
	(0.0734)		(0.0872)		(0.125)
Physical Integrity Index		0.0173		−0.165 ***		−0.183 **
		(0.0314)		(0.0517)		(0.0711)
Largest discriminated group	1.213 *	1.109 *	−1.029	−0.894	1.191 **	1.288 **
	(0.664)	(0.618)	(0.879)	(1.009)	(0.592)	(0.612)
Negative Horizontal inequality	0.0716	−0.0533	0.163 **	0.193 ***	0.270	0.321
	(0.0985)	(0.0932)	(0.0746)	(0.0745)	(0.168)	(0.196)
Positive horizontal inequality	0.223	0.0560	−0.431 ***	−0.358 **	−0.399	−0.225
	(0.217)	(0.126)	(0.166)	(0.164)	(0.510)	(0.588)
Vertical inequality	−0.00651	−0.00608	−0.00707	0.000858	−0.00468	0.00404
	(0.00787)	(0.00835)	(0.0106)	(0.00998)	(0.0188)	(0.0186)
Constant	−1.555	−1.254	−1.991	−2.753 *	8.643 ***	7.813 ***
	(1.101)	(1.172)	(1.650)	(1.621)	(2.693)	(2.715)
Non-violent protest	YES	YES	YES	YES	YES	YES
Violent protest			YES	YES	YES	YES
Terrorist attacks					YES	YES
Lagged DV	YES	YES	YES	YES	YES	YES
Controls	YES	YES	YES	YES	YES	YES
Observations	1482	1470	1287	1276	1356	1344
Model 1 inflation equation (Equation (1))—zero-inflated negative binomial—baseline risk of no conflict
	PTS	CIRI	PTS	CIRI	PTS	CIRI
	Risk of Violent protest	Risk of Violent protest	Risk of Terrorist attacks	Risk of Terrorist attack	Risk of Civil war deaths	Risk of Civil war deaths
Protest repression	−0.948 **	−0.942 ***
	(0.377)	(0.310)
PTS	0.439		−0.0507		1.395 ***
	(0.290)		(0.171)		(0.245)
Physical Integrity Index		0.0954		0.0278		0.700 ***
		(0.134)		(0.0968)		(0.107)
Size of largest discriminated group	1.835	1.423	−3.467 ***	−2.971 **	−2.541	−2.524
	(1.530)	(1.500)	(1.230)	(1.186)	(1.882)	(1.710)
Negative Horizontal inequality	0.620 ***	−1.434	0.428	0.440	−0.657 ***	−0.739 ***
	(0.220)	(1.571)	(0.345)	(0.338)	(0.225)	(0.179)
Positive horizontal inequality	1.194 **	−0.735	−1.480	−1.235	1.021 *	0.885 *
	(0.560)	(1.526)	(1.032)	(1.073)	(0.562)	(0.487)
Vertical inequality	−0.152 ***	−0.157 ***	−0.00231	0.00458	0.0109	0.00546
	(0.0323)	(0.0283)	(0.0166)	(0.0162)	(0.0257)	(0.0250)
Constant	15.73 ***	21.12 ***	4.828 *	3.487	−5.898 *	−5.282 *
	(3.958)	(4.619)	(2.517)	(2.681)	(3.118)	(3.127)
/lnalpha	−0.456 **	−0.415 ***	0.375 ***	0.377 ***	−0.0247	−0.0252
	(0.181)	(0.155)	(0.0746)	(0.0763)	(0.146)	(0.135)
Non-violent protest	YES	YES	YES	YES	YES	YES
Violent protest			YES	YES	YES	YES
Terrorist attacks					YES	YES
Lagged DV	YES	YES	YES	YES	YES	YES
Controls	YES	YES	YES	YES	YES	YES
Observations	1482	1470	1287	1276	1356	1344

Coefficients for the inflation equation (Equation (1)) correspond to the probability of experiencing a lower risk of violence. Positive coefficients indicate a lower chance of seeing conflict onset while negative coefficients indicate a greater chance of conflict onset. /lnalpha is the over dispersion parameter which can be interpreted as a measure of conflict contagion. Robust standard errors in parentheses. Two-tail test. *** p < 0.01, ** p < 0.05, * p < 0.1.

presents the main findings from our zero-inflated negative binomial models. The full table can be found in the accompanying Appendix A. These models have two components. The first equation measures the risk of experiencing conflict and the second equation measures the number of conflict events. For each of our variables, we are able to test whether they reduce the baseline risk of experiencing conflict, and whether they reduce the number of conflict events. We expect a negative relationship between human rights respect and conflict in the outcome equation (Equation (2)), and a positive relationship in the risk equation (Equation (1)). We expect a positive relationship between inequality and conflict in the outcome equation, and a negative relationship in the risk equation. Finally, we expect a negative relationship between civil and political rights respect and conflict in the outcome equation, and a positive relationship in the risk equation.

Table 2 also shows the results of our first models exploring the relationship between inequality and conflict. These results allows us to see whether inequality and human rights respect have independent and significant effects on conflict, which we find they do. A positive coefficient in the first (inflation) equation indicates that a country is less likely to experience conflict. A positive coefficient in the second (outcome) equation indicates that a country is more likely to experience a greater number of events.

Figure 2 and Figure 3 plot the predictions from our first model across the range of the Physical Integrity Index and the Political Terror Scale. The first thing to notice is that across these two measures our findings are largely the same. As respect for physical integrity rights increases, we see fewer terror attacks (top left), and at very high levels of these rights our predictions have less uncertainty. Our predictions for civil war deaths are in the top right. As respect for physical integrity rights increases, we are likely to see fewer civil war deaths all else equal. The different confidence intervals indicate that we are most confident that high levels of respect for physical integrity rights will lead to less internal violence of all types. Finally, across both scales the probability that a country avoids a civil war approaches 100% at the highest levels of respect for physical integrity rights. These predictions contain tight confidence intervals, giving us more confidence in our findings.

Figure 4 examines the predictions from model 1 at different values for the size of the largest discriminated group holding all else constant. In the top left, we see that as the size of the largest discriminated group increases there is a rise in violent protests. At higher levels, our predictions are less certain (larger confidence intervals) in part because there are fewer countries with discriminated groups which make up a very large portion of the population. However, moving from 0% to around 20% increases the number of violent protests by about 25%. Civil war deaths look very similar, as the size of the largest discriminated group increases, we see an increase in the number of civil war deaths (top right). The confidence intervals around these predictions are once again quite large at higher levels of our independent variable. The most pronounced predictions come from our predictions concerning the risk of being targeted for a terror attack (bottom left). When a country has a discriminated group that makes up 30% of the population or more, it is almost certain to experience a terror attack. The probability of avoiding a terror attack is almost zero and our model is very confident in these predictions.

Figure 5 examines negative horizontal inequality and the predictions from model 1. As negative horizontal inequality increases, we also see a rise in the risk of violent protests. These predictions are only significant for the model with the political terror scale and the confidence intervals are rather large. Thus, this finding undermines support for our fifth hypothesis. We also find that as horizontal inequality increases (top right) we see a slight increase in the number of terror attacks with uncertainty about our predictions increasing as horizontal inequality increases.

The most confident predictions we have pertain to negative horizontal inequality and the probability of avoiding a civil war. As inequality increases, the probability of avoiding civil war declines from about 87% at the lowest levels of inequality to about 75% at the highest levels. A 10% increase in the probability of civil war is quite significant given how rare civil war onset is. We chose only to plot the predictions from negative horizontal inequality even though positive horizontal inequality produces similar findings though a bit weaker. It is telling that both are statistically significant with negative horizontal inequality indicating the extent of material inequality for the poorest societal group and positive horizontal inequality indicating the amount of resources taken by the wealthiest group in society.

8.3. Respect for Women’s Rights and Four Physical Integrity Rights: Zero-Inflated Negative Binomial Modelh

Table 3. Types of Physical Integrity Rights, Women’s Rights and Internal Conflict.

Model 2. Zero-inflated negative binomial regression—1990–2015
	Equation (2)	Equation (1)	Equation (2)	Equation (1)	Equation (2)	Equation (1)
	No. of	Risk	No. of	Risk	No. of	Risk
	Violent protests	Violent protest	Terrorist attacks	Terrorism	Civil war deaths	Civil war
Disappearances	0.0817	−0.396	−0.361 ***	0.477 ***	−0.164	0.732 ***
	(0.0639)	(0.263)	(0.0911)	(0.182)	(0.130)	(0.188)
Extrajudicial killings	−0.00365	0.839 ***	−0.0707	0.206	−0.142	0.735 ***
	(0.0779)	(0.230)	(0.125)	(0.128)	(0.182)	(0.183)
Political imprisonment	0.00829	−0.0837	−0.254 **	0.300 *	−0.0145	0.652 ***
	(0.0831)	(0.232)	(0.101)	(0.180)	(0.135)	(0.219)
Torture	0.0208	0.180	−0.218 *	−0.237	−0.737 ***	−0.0840
	(0.0814)	(0.237)	(0.117)	(0.169)	(0.233)	(0.227)
Women’s rights	−0.130 **	0.121	−0.381 ***	−0.209 *	0.164	0.129
	(0.0506)	(0.159)	(0.0960)	(0.119)	(0.116)	(0.139)
Constant	−3.009 ***	−2.327	−2.847 **	2.228	6.916 ***	−0.973
	(0.651)	(2.369)	(1.350)	(1.706)	(1.778)	(2.327)
/lnalpha		0.0927		0.694 ***		0.230 **
		(0.127)		(0.0828)		(0.111)
Non-violent protest	YES	YES	YES	YES	YES	YES
Violent protest			YES	YES	YES	YES
Terrorist attacks					YES	YES
Lagged DV	YES	YES	YES	YES	YES	YES
Controls	YES	YES	YES	YES	YES	YES
Observations	3397	3397	3156	3156	3228	3228

Coefficients for the inflation equation (Equation (1)) correspond to the probability of experiencing a lower risk of violence. Positive coefficients indicate a lower chance of experiencing conflict onset while negative coefficients indicate a greater chance of conflict onset. /lnalpha is the over dispersion parameter which can be interpreted as a measure of conflict contagion. Robust standard errors in parentheses. Two-tail test. *** p < 0.01, ** p < 0.05, * p < 0.1.

below also shows that the type of repression that states engage in has varying effects on different types of conflict. When governments refrain from engaging in disappearances, they are less likely to experience civil war or terrorist attacks against them. They are also likely to experience fewer terrorist attacks when they do occur. Governments who kill their citizens are at greater risk of facing violent protests and civil war. When governments engage in political imprisonment, they are more likely to experience civil war and terrorism. They are also likely to experience more terrorist attacks. The use of torture increases the number of terrorist attacks and civil war deaths. Finally, women’s rights are associated with a decline in the number of violent protests and the number of terrorist attacks. When governments respect women’s rights, they are also less likely to experience a terrorist attack.

These findings are generally consistent with earlier research showing that all types of physical integrity abuse increase the onset and escalation of conflict. Our findings are more complex. For example, when a government engages in extrajudicial killing, the likelihood increases that there will be at least one violent protest. But none of the types of repression of physical integrity rights increases the number of violent protests that take place. Only lower respect for women’s rights was associated with an increase in the number of violent protests. Repression of protesters is also associated with an increase in violent protest.

Both the onset and escalation of terrorism are closely tied to all the human rights variables in our model in ways we had hypothesized. The one exception being that greater respect for women’s rights increases the risk of terrorism, though it decreases the number of terrorist events. All forms of physical integrity rights violations were associated with an increased likelihood that civil war would begin (except torture). Only government torture was related to the escalation of civil war (increase in battle deaths). Our first empirical model therefore shows support for Hypothesis 1.

Our findings for Women’s rights and conflict are generally supportive of our third hypothesis. Respect for women’s rights reduces the number of violent protests as well as the number of terror attacks. However, countries which respect women’s rights have a higher baseline likelihood of the onset of a terror attack. If women’s rights are a proxy for societal inequality, then this may indicate increased tensions between dominant and non-dominant societal groups which may be responsible for the rise in terrorism.

A rise in women’s status or the status of other discriminated groups may increase the use of terrorism by those who are threatened by changing demographics or changing societal norms. For example, Phumzile Mlambo-Ngcuka (the United National Under-Secretary-General and Executive Director of UN Women) argues that terrorist groups have been increasingly targeting women’s rights and women as a terror tactic. Attacks on women’s social, political, and economic rights have increased in recent decades which is consistent with our findings (Mlambo-Ngcuka). However, even if the risk of being targeted for a terror attack increases, countries that respect women’s rights experience fewer terror attacks. This may indicate that where women have rights and are able to exercise those rights, terror groups face higher costs for successfully carrying out terror campaigns.

Figure 6 shows the predictions for the women’s rights variables. As the level of women’s rights respect rises, we see a marked decline in violent protest (top left). Moving from zero respect to full respect for women’s rights reduces the predicted number of violent protests by about 0.7. Given that on average a country experiences only 0.8 violent protests in a year, this is a rather large reduction. Similarly, respect for women’s rights reduces the number of predicted terrorist attacks (top right) from around 17 attacks a year at no respect for women’s rights to about two attacks a year at the highest levels of respect for women’s rights. The uncertainty surrounding the predictions for terrorist attacks are quite a bit more confident than those for violent protest. However, as respect for women’s rights increases, a country is less likely to avoid a terrorist attack. The probability of avoiding a terror attack falls from about 47% with no respect for women’s rights to about 29% with full respect of women’s rights. So, respect for women’s rights increases the likelihood of seeing at least one attack, but reduces the number of terrorist attacks a country is likely to see. We take this as moderate support for Hypothesis 3.

8.4. Respect for Civil and Political Rights—Zero-Inflated Negative Binomial Model

Our findings in model 3 are largely the same as those in models 1 and 2. The four physical integrity rights together predict a reduction in the number of terror events and an increase in the likelihood of not experiencing a form of violent internal conflict. We therefore once again find support for our first hypothesis. Similarly, women’s rights operate in the same manner as model 2. Greater respect for women’s rights decreases the number of violent protests and the number of terror attacks though it increases the risk of being targeted for a terror attack. We therefore once again find support for our fifth hypothesis.

Turning to our civil and political rights, our findings are mixed. Respect for freedom of association is associated with a lower number of violent protests though a higher risk of protest onset. This may indicate that free association and assembly decreases the cost of organizing protests. As the number of protests increases so does the likelihood that one turns violent either as a response to state repressive tactics or a strategic or emotional decision by protests. However, in countries where citizens have the right to freely assemble, they experience fewer violent protests all else equal.

Freedom of foreign movement is associated with a rise in the number of terror attacks. This makes sense as the ability to move across international borders may reduce the organizational and logistic costs of terror operations. However, we find no effect for freedom of domestic movement. Free speech is also associated with a rise in the number of terror attacks.

Overall, we find some evidence that respect for civil and political rights increases the likelihood of experiencing domestic conflict. This is consistent with past work arguing that civil and political rights reduce the coordination costs for collective dissent. We therefore find modest support for Hypothesis 4.

We also find support for our second hypothesis. In models 2 and 3, we see that political imprisonment and disappearances produce an increase in more forms of internal conflict than torture or extrajudicial killings (

Table 4. Civil and Political Liberties and Internal Conflict.

Model 3. Zero-inflated negative binomial regression—Civil and Political Liberties 1990−2015
	Equation (2)	Equation (1)	Equation (2)	Equation (1)	Equation (2)	Equation (1)
	No. of	Risk	No. of	Risk	No. of	Risk
VARIABLES	Violent protests	Violent protest	Terrorist attacks	Terrorist attacks	Civil war deaths	Civil war
Protester repression	0.00527	0.566 *
	(0.0295)	(0.313)
Disappearances	0.0689	−0.399	−0.341 ***	0.425 **	−0.141	0.701 ***
	(0.0646)	(0.269)	(0.0811)	(0.179)	(0.117)	(0.183)
Extrajudicial killings	0.00146	0.890 ***	−0.133	0.189	−0.0768	0.735 ***
	(0.0736)	(0.212)	(0.115)	(0.135)	(0.184)	(0.173)
Political imprisonment	0.0496	−0.0241	−0.119	0.272	0.0188	0.587 ***
	(0.0976)	(0.250)	(0.0902)	(0.172)	(0.110)	(0.186)
Torture	0.0407	0.196	−0.259 **	−0.228	−0.635 ***	−0.0759
	(0.0725)	(0.228)	(0.126)	(0.172)	(0.225)	(0.224)
Women’s rights	−0.112 **	0.147	−0.343 ***	−0.208 *	0.159	0.155
	(0.0520)	(0.154)	(0.0982)	(0.117)	(0.116)	(0.139)
Freedom of association	−0.179 **	−0.548 **	−0.100	−0.0731	0.0383	0.129
	(0.0890)	(0.230)	(0.121)	(0.151)	(0.129)	(0.197)
Foreign movement	0.0453	−0.191	0.289 **	0.284	0.0438	−0.186
	(0.0699)	(0.212)	(0.114)	(0.182)	(0.134)	(0.164)
Domestic movement	0.0858	0.125	0.172	−0.000638	−0.102	0.102
	(0.0679)	(0.174)	(0.105)	(0.154)	(0.0974)	(0.125)
Free speech	0.0177	−0.0314	0.178 *	−0.0519	−0.100	0.212
	(0.0928)	(0.283)	(0.104)	(0.166)	(0.172)	(0.183)
Constant	−2.915 ***	−0.388	−4.499 ***	1.563	6.154 ***	−1.116
	(0.660)	(2.279)	(1.214)	(1.666)	(1.148)	(2.461)
/lnalpha		0.056		0.713 ***		0.238 **
		0.127		0.078		0.122
Non-violent protest	YES	YES	YES	YES	YES	YES
Violent protests			YES	YES	YES	YES
Terrorist attacks					YES	YES
Lagged DV	YES	YES	YES	YES	YES	YES
Controls	YES	YES	YES	YES	YES	YES
Observations	3468	3468	3227	3227	3299	3299

Coefficients for the inflation equation (Equation (1)) correspond to the probability of experiencing a lower risk of violence. Positive coefficients indicate a lower chance of experiencing conflict onset while negative coefficients indicate a greater chance of conflict onset. /lnalpha is the over dispersion parameter which can be interpreted as a measure of conflict contagion. Robust standard errors in parentheses. Two-tail test. *** p < 0.01, ** p < 0.05, * p < 0.1.

).

8.5. Other Findings of Interest

Overall, we find that many of the control variables operated as we expected. Wealthy countries, those experiencing growth, and those with a smaller population saw less internal violent conflict when these variables were significant. Democracy was largely insignificant though in a few models it came up as a significant predictor of conflict in one of the two models for civil war deaths, terrorist attacks, and violent protest onset. These findings are consistent with the coordination or opportunity argument outlined above. However, given that democracy was always significant in one model but not in the other, we are hesitant to read too much into these findings, especially since they are inconsistent with some past work indicating that democracies see less violence than non-democracies. Our findings in this paper also suggest that the way democracy is measured may have a large impact on its relationship to conflict, human rights respect, and inequality.

We find some support for our argument that large numbers of lower cost collective dissent precede higher cost violent conflict. For example, in all but one model, we find that as the number of violent protests increases in the previous year, we are more likely to see an increased risk of and number of violent protests in the current year. There is also some evidence that non-violent protests also predict an increase in terror attacks and civil war deaths. This suggests that when non-violent protest is not successful, or the state responds in ways that are unpopular to this form of collective action, we are more likely to see citizens turn to violence in the future.

We find evidence in about half of our models that a large number of violent protests last year is associated with a rise in the number of terrorist attacks this year. This suggests that violent protest may be a useful predictor of where we will see terrorism, especially in states where the grievances of violent protests are not addressed. We also find that violent protests are associated with a decline in the number of civil war deaths and civil war onset in some models. This may be because those protesting violently are not participating in rebellion and suggests a substitution effect between different violent strategies. Finally, we find that when there are terrorist attacks in the previous year, we are more likely to see civil war onset and a larger number of civil war deaths in the current year. This may be because those using terror strategies successfully are able to launch rebel campaigns or it may be an indication that the use of terrorism by rebel groups prolongs civil wars.

Finally, in every model, we find that if violence of any kind was used in the previous year (a lagged dependent variable) we are more likely to see violence in the current year. This matches up with past research showing that once violence starts it is very hard to stop. We believe that future studies of conflict should investigate in more depth the relationships between different types of conflict and the choice of citizens to use one violent strategy over another as well as how citizens choose to switch between strategies or pursue multiple strategies simultaneously. The evidence we present here suggests that human rights and inequality may present an important factor in explaining these decisions.

8.6. Summary of Findings

Table 5. Factors Associated with Either the Increased Risk of Onset or Greater Numbers of Violent Protests, Terrorism Events, or Civil War Deaths.

	Violent Protests	Acts of Terrorism	Civil War
Lower Level of Respect for Physical Integrity Rights (Index)	No	Yes	Yes
More Disappearances	No	Yes	Yes
More Extrajudicial Killings	Yes	No	Yes
More Political Imprisonment	No	Yes	Yes
More Torture	No	Yes	Yes
Worse Respect for Women’s Rights	Yes	?	No
More State Repression of Protesters	Yes	NA	NA
Freedom of Association and Assembly	?	No	No
Freedom of Foreign Movement	No	Yes	No
Freedom of Speech	No	Yes	No
Higher Level of Negative Horizontal Inequality	No	Yes	Yes
Higher Level of Positive Horizontal Inequality	No	No	No
A Large Group of People Discriminated Against in Society	Yes	Yes	Yes
Higher Level of Vertical Inequality	No	No	No

Note: “?” means that there were inconsistent results among the results of the statistical models that we used or that the results for onset and greater number of events were statistically significant but inconsistent. “No” means that results for all models were statistically insignificant or in a direction we did not anticipate. “NA” means not applicable, because the relationship was not tested.

summarizes our findings concerning the effects of human rights violations and horizontal inequality on all three types of internal conflict. Worse respect for physical integrity rights contributed to explanations of all three types of conflict. Repression of protesters is also associated with an increase in violent protests. Poor respect for women’s rights contributed to an increase in the likelihood of violent protests as well as a higher number of terror attacks, though it led to a decrease in the onset of terrorism and had no effect on civil war. Our indicators of horizontal inequality and discrimination helped explain all three types of conflict. Countries with a large discriminated group saw a rise in all three types of conflict. We also find that the presence of positive horizontal inequality (an elite or rich class with more resources than everyone else) does not increase conflict. However, the existence of negative horizontal inequality (a group that is significantly worse off than the rest of society) does lead to an increase in terrorism and civil war. We also find that freedom of speech and freedom of foreign movement are both associated with a rise in acts of terrorism, while freedom of association and assembly has a mixed effect on whether we see violent protests.

9. Discussion

We find that several types of violations of human rights and the existence of large discriminated groups and negative horizontal inequalities in societies independently produce an increased risk of the onset and escalation of several types of violent internal conflict. Previous research shows that negative horizontal inequality alone makes the onset and escalation of civil war more likely (Cederman et al. 2013). However, this is the first study to show that both horizontal inequality and violations of human rights each have an independent effect as drivers of internal conflict, even when controlling for the effects of the other. We also find that the type of inequality and its distribution in society are important for studies of inequality and conflict. Positive horizontal inequality seems to reduce conflict, suggesting that the concentration of income among elites is less likely to generate conflict than the size of discriminated groups and the share of income that discriminated groups receive.

Violations of physical integrity rights and women’s rights were found to be additional drivers of processes that led to civil war. Furthermore, all types of physical integrity violations contributed to the explanation of civil war. Our findings concerning the onset or escalation of terrorism were almost as strong. Walsh and Piazza (2010) had reported a strong relationship between government violations of personal security rights and various forms of violent internal conflict. These results are consistent with theirs, though they did not control for horizontal inequality, which contributes to the explanation of terrorism.

Previous research had demonstrated a strong relationship between violation of women’s’ rights and higher incidence of various forms of violent internal conflict (Caprioli 2005; Harris and Milton 2016; Hudson et al. 2009; Melander 2005a). This study found support for the idea that repression of women’s rights leads to a greater number of violent protests. We found that violations of women’s rights increase the likelihood of experiencing terrorism, but also reduce the number of attacks. Scholars disagree about why violations of women’s rights lead to more conflict, so more attention should be given to the empirical implications of alternative theoretical arguments.

Some of our findings are directly relevant to the current policy debate over whether there is a trade-off between liberty and security. The results provide some evidence that the trade-off is real as it pertains to the risk of domestic terrorism. In particular, our findings suggest that societies that respect citizens’ rights to freedom of speech and press and allow freedom for citizens to leave their country and to return face greater risks of suffering terrorism, other things equal.

The results of this study, coupled with the results reported by Bell et al. (2013) suggest that it would be useful to carefully investigate the following proposition: The risk of stimulating more domestic terrorism is greatest in poor, low capacity states that violate physical integrity rights and/or have deep horizontal inequalities. Under such circumstances, citizens are likely to have grievances against their governments and be able to openly express their grievances and mobilize government opposition.

Previous research on the relationship between human rights and internal conflict each examined one type of right on one type of internal conflict—violent protest, terrorism, or civil war. We ask whether human rights violations matter for all three types of conflict. We found that similar types of human rights violations were important factors in explaining all three types of internal conflict.

We also found some support for our argument that lower cost collective dissent events preceded higher cost violent conflict events. For example, in our Appendix A models, we find that non-violent protests last year predict violent protests this year. Violent protests this year predict terrorist attacks next year, and finally that terrorist attacks this year predict civil war next year. In every model, we found that if violence of any kind was used in the previous year (a lagged dependent variable) we are more likely to see violence in the current year. This matches up with past research showing that once violence starts it is very hard to stop. We believe future studies of conflict should investigate in more depth the relationships between different types of conflict and the choice of citizens to use one violent strategy over another as well as how citizens choose to switch between strategies or pursue multiple strategies simultaneously. The evidence we present here suggests that human rights and inequality may be important factors in explaining these decisions.

Future research should explore another related argument—that the highest probability for internal violence occurs when governments violate personal security rights in a deeply horizontally divided society. In that instance, some particular ethnic or religious group is likely to be discriminated against and deprived of its rights. That group is likely to rebel. Thus, violent internal conflicts are more likely to occur and/or escalate. In other words, we think that respecting human rights is likely to be particularly important as a way to ensure peace in societies that are deeply divided in terms of religion and ethnicity as opposed to societies that are not. We have not found support for this argument in analyses we have conducted so far, but we consider this idea to be a particularly fruitful avenue for future research.

Human rights and peace are mutually reinforcing. Future research should focus on determining the stronger causal direction of the relationship between human rights and internal violent conflict within countries. There are three possibilities: (1) respect for human rights causes a higher level of peace and stability; (2) peace and stability causes a higher level of respect for human rights; or (3) the relationship between human rights and peace is spurious. That is, both human rights and peace are caused by some other factor. This paper contributes to that long-term research agenda by focusing on some important and relatively neglected arguments, suggesting that respect for various human rights leads to a higher level of peace and stability and by providing some evidence in support of those arguments.