Determinants of Domestic Terrorism: An Examination of Ethnic Polarization and Economic Development

ABSTRACT

Many scholars have sought to explain why countries with ethnically heterogeneous populations experience higher levels of political violence, but these studies have produced mixed findings. Unlike most studies that use ethno-linguistic fractionalization indices to examine this relationship, we argue that ethnic polarization is a more appropriate measure to assess the role of ethnicity as a causal factor of domestic terrorism. This paper hypothesizes that high ethnic polarization influences the incidence of domestic terrorism, particularly when intervening economic factors are present. To test three hypotheses, we use negative binomial regression to model data from the Global Terrorism Dataset, World Bank, and the Reynal-Querol (RQ) ethnic polarization index of 116 countries between 1970 and 2012. Our findings show that terrorism is more likely to emerge in societies with high ethnic polarization and economic malaise.

KEYWORDS:

• Domestic terrorism
• economic malaise and terrorism
• ethnic polarization
• ethnic terror
• heterogeneous populations

Supplementary materials

Supplementary materials for the article are available on the publisher’s website.

Notes

1. Daniel Byman, “The Logic of Ethnic Terrorism,” Studies in Conflict and Terrorism 21, no. 1 (1998): 149–69; Martha Crenshaw, “The Causes of Terrorism,” Comparative Politics 13, no. 4 (1981): 379–99.

2. Sambuddha Ghatak, “Willingness and Opportunity: A Study of Domestic Terrorism in the Post-Cold War South Asia,” Terrorism and Political Violence (2014): 1–23; Roger D. Petersen, Understanding Ethnic Violence (Cambridge, UK: Cambridge University Press, 2002); Roberta Senechal de la Roche, “Collective Violence as Social Control,” Sociological Forum 11, no. 1 (1996): 97–128; Donald L. Horowitz, Ethnic Groups in Conflict (Berkeley, CA: University of California Press, 1985); Chaim Kaufman, “Possible and Impossible Solutions to Ethnic Civil Wars,” International Security 20, no. 4 (1996): 136–75; Krisztina Kis-Katos, Helge Liebert, and Gunther G. Schulze, “On the Heterogeneity of Terror,” European Economic Review 68 (2014): 116–36.

3. James Fearon and David Laitin, “Ethnicity, Insurgency, and Civil War,” American Political Science Review 97, no. 1 (2003): 75–90.

4. Alberto Abadie, “Poverty, Political Freedom, and the Roots of Terrorism,” National Bureau of Economic Research, Working Paper No. 10859 (2004).

5. Seung-Whan Choi and James A. Piazza, “Ethnic Groups, Political Exclusion and Domestic Terrorism,” Defence and Peace Economics 27, no. 1 (2014): 37–63.

6. Alberto Alesina et al. “Fractionalization,” Journal of Economic Growth 8, no. 2 (2003): 155–94; Alberto Alesina and Eliana La Ferrara, “Ethnic Diversity and Economic Performance,” Journal of Economic Literature 43, no. 3 (2005): 762–800.

7. Marta Reynal-Querol, “Ethnicity, Political Systems, and Civil Wars,” Journal of Conflict Resolution 46, no. 1 (2002): 29–54; Jose Montalvo and Marta Reynal-Querol, “Ethnic Polarization, Potential Conflict, and Civil Wars,” The American Economic Review 95, no. 3 (2005): 796–816.

8. Walter Enders, Gary A. Hoover, and Todd Sandler, “The Changing Nonlinear Relationship between Income and Terrorism,” Journal of Conflict Resolution 60, no. 2 (2016): 195–225.

9. For an analysis of reasons to distinguish between domestic and transnational terrorism see Todd Sandler, “The Analytical Study of Terrorism: Taking Stock,” Journal of Peace Research, 51, no. 2 (2014): 257–71; James Piazza, “Poverty, Minority Economic Discrimination, and Domestic Terrorism,” Journal of Peace Research 48, no. 3 (2011): 339–53; Walter Enders, Todd Sandler, and Khusrav Gaibulloev, “Domestic versus Transnational Terrorism: Data, Decomposition, and Dynamics,” Journal of Peace Research 48, no. 3 (2011): 319–37.

10. Roger Brubaker and David D. Laitin, “Ethnic and Nationalist Violence,” Annual Reviews Sociology 24 (1998): 425.

11. Nicholas Sambanis, “Terrorism and Civil War,” in Terrorism and Economic Development (Cambridge, UK: Cambridge University Press, 2008); Fearon and Laitin, “Ethnicity, Insurgency, and Civil War” (see note 3 above); Kaufman, “Possible and Impossible” (see note 1 above).

12. David Lake, “Rational Extremism,” Dialog-IO Spring (2002): 15–29; Sambanis, “Terrorism and Civil War” (see note 11 above); Joseph L. Soeters, Ethnic Conflict and Terrorism (London, UK: Routledge, 2005); Stathis Kalyvas, “The Paradox of Terrorism in Civil War,” Journal of Ethics 8, no. 1 (2004): 97–138; Brock Blomberg, Gregory D. Hess, and Athanasios Orphanides, “The Macroeconomic Consequences of Terrorism,” Journal of Monetary Economics 51 (2004): 1007–32.

13. Michael Findley and Joseph K. Young, “Terrorism and Civil War: A Spatial and Temporal Approach to a Conceptual Problem,” Perspectives on Politics 10, no. 2 (2012): 285–305, 285.

14. Jakana Thomas, “Rewarding Bad Behavior,” American Journal of Political Science 58, no. 4 (2014): 804–18.

15. Byman, “The Logic of Ethnic Terrorism,” (see note 1 above), 150.

16. Ibid.

17. Brock Blomberg, Gregory D. Hess, and Akila Weerapana, “An Economic Model of Terrorism,” Conflict Management and Peace Science 21, no. 1 (2004): 17–28.

18. Byman, “The Logic of Ethnic Terrorism” (see note 1 above), 154.

19. Robert A. Pape, “The Strategic Logic of Suicide Terrorism,” The American Political Science Review 97, no. 3 (2003): 343–61.

20. Ghatak, “Willingness and Opportunity” (see note 2 above) uses a heterogeneity cost composite variable from Vanhanen, ECDIS Index 2009. Vanhanen data is limited to 2003–2009.

21. The scope is limited to 1982–1987. Atin Basuchoudhary and William F. Shughart II, “On Ethnic Conflict and the Origins of Transnational Terrorism,” Defence and Peace Economics. 21, no. 1 (2008): 65–87.

22. Peter Kurrild-Klitgaard, Mogens K. Justesen, and Robert Klemmensen, “The Political Economy of Freedom, Democracy and Transnational Terrorism,” Public Choice 128, no. 1 (2006): 23–53.

23. Piazza (2006) and Fearon and Laitin (2003) revealed inconsistent statistical findings using ELF to model the relationship between varied types of conflict and the level of ethnic heterogeneity in a population. James Piazza, “Rooted in Poverty? Terrorism, Poor Economic Development, and Social Cleavages,” Terrorism and Political Violence 18 (2006): 159–77; Fearon and Laitin, “Ethnicity, Insurgency, and Civil War” (see note 3 above). See also Alan B. Krueger and Jitka Maleckova, “Education, Poverty, and Terrorism,” Journal of Economics Perspectives 17, no. 4 (2002): 119–44; William Easterly and Ross Levine, “Africa’s Growth Tragedy: Policies and Ethnic Divisions,” The Quarterly Journal of Economics 112, no. 4 (1997): 1203–50.

24. Senechal de la Roche, “Collective Violence” (see note 1 above); Donald Black, “The Geometry of Terrorism,” Sociological Theory 22, no. 1 (2004): 14–25.

25. Joan Esteban and Debraj Ray, “On the Measurement of Polarization,” Econometrica 62, no. 4 (1994): 819–51; Joan Esteban and Gerald Schneider, “Polarization and Conflict,” Journal of Peace Research 45, no. 2 (2008): 131–41.

26. See Abadie, “Poverty, Political Freedom, and the Roots of Terrorism” (see note 4 above); Kurrild-Klitgaard et al., “The Political Economy” (see note 22 above).

27. Esteban and Schneider, “Polarization and Conflict” (see note 25 above), 133.

28. Senechal de la Roche, “Collective Violence” (see note 1 above).

29. Reynal-Querol, “Ethnicity, Political Systems, and Civil War” (see note 7 above); Esteban and Schneider, “Polarization and Conflict” (see note 25 above); Barry Weingast, “Constructing Trust: The Political and Economic Roots of Ethnic and Regional Violence,” in Institutions and Social Order (Ann Arbor, MI: University of Michigan Press, 1998).

30. Joan Esteban and Debraj Ray, “Polarization, Fractionalization and Conflict,” Journal of Peace Research 45, no. 2 (2008): 163–82; Joan Esteban and Debraj Ray, “On the Salience of Ethnic Conflict,” American Economic Review 98, no. 5 (2008): 2185–2202.

31. Blomberg et al., “An Economic Model” (see note 17 above).

32. Cost for incidents of terrorism are low, where poor socioeconomic conditions exist.

33. Andreas Freytag, Jen J. Kruger, Daniel Meierrieks, and Friedrich Schneider, “The Origins of Terrorism,” European Journal of Political Economy 27 (2011); Enders et al., “The Changing Nonlinear Relationship” (see note 8 above); Efraim Benmelech, Claude Berrebi, and Esteban Klor, “Economic Conditions and the Quality of Suicide Terrorism,” Journal of Politics 74, no. 1 (2012): 1–16.

34. Piazza, “Rooted in Poverty” (see note 23 above); Piazza, “Poverty, Minority Economic Discrimination, and Domestic Terrorism” (see note 9 above); Krueger and Maleckova, “Education, Poverty, and Terrorism” (see note 23 above); Abadie, “Poverty, Political Freedom, and the Roots of Terrorism” (see note 4 above); Quan Li, “Does Democracy Promote or Reduce Transnational Terrorist Incidents,” Journal of Conflict Resolution 49, no 2 (2005): 278–97; Quan Li and Drew Schaub, “Economic Globalization and Transnational Terrorism,” Journal of Conflict Resolution 48, no. 2 (2004): 230–58; Enders et al., “The Changing Nonlinear Relationship” (see note 8 above).

35. Axel Dreher and Martin Gassebner, “Does Political Proximity to the U.S. Cause Terror?,” Economic Letters 99 (2008): 29.

36. Li and Schaub, “Economic Globalization” (see note 34 above).

37. Brian Lai, “Draining the Swamp: An Empirical Examination of the Production of International Terrorism, 1968–1998,” Conflict Management and Peace Science 24 (2007): 297–310.

38. Claude Berrebi, “Evidence about the Link between Education, Poverty and Terrorism among Palestinians,” Peace Economics, Peace Science and Public Policy 13, no. 1 (2007): 2–39; Benmelech, Berrebi, and Klor, “Economic Conditions” (see note 33 above).

39. Piazza, “Poverty, Minority Economic Discrimination, and Domestic Terrorism” (see note 9 above); Martin Gassebner and Simon Luechinger, “Lock, Stock, and Barrel,” Public Choice 149, no. 3–4: 235–61.

40. Freytag et al., “The Origins of Terrorism” (see note 33 above).

41. Enders et al., “The Changing Nonlinear Relationship” (see note 8 above), 26.

42. Henrik Urdal, “Population, Resources, and Political Violence,” Journal of Conflict Resolution 52, no. 4 (2008): 590–617; Monica Toft, “Population Shifts and Civil War,” International Interactions 33 (2007): 243–69; Gary LaFree and Bianca Bersani, “County-Level Correlates of Terrorist Attacks in the United States,” Criminology and Public Policy 13, no. 3 (2014): 455–81; Ghatak, “Willingness and Opportunity” (see note 2 above); Sambanis, “Terrorism and Civil War” (see note 11 above); Tanja Ellingsen, “Colorful Community or Ethnic Witches’ Brew? Multiethnicity and Domestic Conflict during and after the Cold War,” Journal of Conflict Resolution 44, no. 2 (2000): 228–49. With the exception of Ghatak, these studies assess the role of multi-ethnic societies and armed conflict. None use polarization as a measure of ethnic grievances.

43. Krueger and Maleckova, “Education, Poverty, and Terrorism” (see note 23 above).

44. Paul Collier and Anke Hoeffler, “Greed and Grievance in Civil War,” Oxford Economic Papers 56 (2004): 563–95; Horowitz, Ethnic Groups (see note 2 above).

45. Daniel Meierrieks and Thomas Gries, “Causality between Terrorism and Economic Growth,” Journal of Peace Research 50, no. 1 (2013): 91–104; Ghatak, “Willingness and Opportunity” (see note 2 above); National Consortium for the Study of Terrorism and Responses to Terrorism (START), “Global Terrorism Database” (2014 data file), http://www.start.umd.edu/gtd

46. Kis-Katos et al., “On the Heterogeneity of Terror” (see note 2 above), 118; Basuchoudhary and Shughart, “On Ethnic Conflict” (see note 21 above); Urdal, “Population, Resources, and Political Violence” (see note 42 above).

47. Ibid. For examples of underrepresentation and terrorism in democratic systems see Dennis Foster, Alex Braithwaite, and David Sobek, “There Can Be No Compromise: Institutional Inclusiveness, Fractionalization and Domestic Terrorism,” British Journal of Political Science 43, no. 3 (2013): 541–57; Deniz Aksoy and David Carter, “Electoral Institutions and the Emergence of Terrorist Groups,” British Journal of Political Science 44, no. 1 (2014): 181–204.

48. Ariel Merari, “Terrorism as a Strategy of Struggle,” Terrorism and Political Violence 11, no. 4 (1999): 52–65, 59.

49. Opportunity for political participation, plural ethnic groups, and divergence of group goals can create commitment problems for organized violence. Martha Crenshaw, “Democracy, Commitment Problems and Managing Ethnic Violence: The Case of India and Sri Lanka,” Terrorism and Political Violence 12, no. 4 (2000): 135–59; Foster, Braithwaite, and Sobek, “There Can Be No Compromise” (see note 47 above); Aksoy and Carter, “Electoral Institutions” (see note 47 above).

50. Kis-Katos et al., “On the Heterogeneity of Terror” (see note 2 above), 131.

51. Summary available at http://guardian.co.tt/news/general/2009/10/06/judge-bakr-face-sedition-trial

52. Daurius Fiqueira, Jihad in Trinidad and Tobago, 27 July 1990 (Lincoln, NE: iUniverse Press, 2002). Trinidad’s ethnic distribution is East Indian (43.4%), African (34.2%), mixed (15.3%) (CIA, 2011).

53. Petersen, Understanding Ethnic Violence (see note 2 above).

54. Pape, “The Strategic Logic” (see note 19 above), 349.

55. Mia Bloom, Dying to Kill (New York, NY: Columbia University Press, 2007), 79.

56. Iro Aghedo and Oarhe Osumah, “The Boko Haram Uprising: How Should Nigeria Respond?,” Third World Quarterly 33, no. 5 (2012).

57. Gaurav Ghose and Patrick James, “Third-Party Intervention in Ethno-Religious Conflict,” in Perspectives on Contemporary Ethnic Conflict, edited by Santosh C. Saha (Boulder, CO: Rowman and Littlefield, 2006).

58. Urdal, “Population, Resources, and Political Violence” (see note 42 above); Toft, “Population Shifts” (see note 42 above); Donald Horowitz, The Deadly Ethnic Riot (Berkeley, CA: University of California Press, 2001); Myron Weiner and Michael S. Teitelbaum, Political Demography, Demographic Engineering (New York, NY: Bergahn, 2001).

59. Urdal, “Population, Resources, and Political Violence” (see note 42 above), 597.

60. Horowitz, Ethnic Groups (see note above), 196.

61. Alberto Alesina and Enrico Spolaore, The Size of Nations (Cambridge, MA: MIT Press, 2003).

62. Kimberley Marten, Warlords: Strong Arm Brokers in Weak States (Ithaca, NY: Cornell University Press, 2012).

63. Stephen Saideman and R. William Ayres, “Determining the Causes of Irredentism,” Journal of Politics 62, no. 4 (2000): 1126–44.

64. Ted Gurr and Barbara Harff, Ethnic Conflict in World Politics (Boulder, CO: Westview, 1994); Ellingsen, “Colorful Community” (see note 42 above); Paul Collier, “Economic Causes of Civil Conflict and Their Implications for Policy,” World Bank (2006), http://users.ox.ac.uk/~econpco/research/pdfs/

65. Marten, Warlords (see note 62 above); David Von Drehle, “The War on ISIS,” Time, March 9, 2015, 24–30.

66. Ghose and James, “Third Party Intervention” (see note 57 above).

67. Brandon M. Boyland, “What Drives Ethnic Terrorist Campaigns? A View at the Group Level of Analysis,” Conflict Management and Peace Science 33, no. 3 (2016): 250–72; Choi and Piazza, “Ethnic Groups, Political Exclusion and Domestic Terrorism” (see note 5 above); Sambuddha Ghatak and Aaron Gold, “Development, Discrimination, and Domestic Terrorism: Looking Beyond a Linear Relationship,” Conflict Management and Peace Science (2015): 10.1177/0738894215608511; Aksoy and Carter, “Electoral Institutions” (see note 47 above); Piazza, “Poverty, Minority Economic Discrimination, and Domestic Terrorism” (see note 9 above).

68. Horowitz, Ethnic Groups (see note 2 above); Montalvo and Reynal-Querol, “Polarization” (see note 7 above).

69. Susan Olzak, The Dynamics of Ethnic Competition and Conflict (Redwood, CA: Stanford Press, 1992); Krisztina Kis-Katos, Helge Liebert, and Gunther G. Schulze, “On the Origin of Domestic and International Terrorism,” European Journal of Political Economy 27 (2011): 17–36; Enders et al., “The Changing Nonlinear Relationship” (see note 8 above); Piazza, “Poverty, Minority Economic Discrimination, and Domestic Terrorism” (see note 9 above).

70. Raul Caruso and Friedrich Schneider, “Brutality of Jihadist Terrorism,” Journal of Policy Modeling 35 (2013): 685–96.

71. Ghatak, “Willingness and Opportunity” (see note 2 above); Piazza, “Poverty, Minority Economic Discrimination, and Domestic Terrorism” (see note 9 above).

72. Ghatak, “Willingness and Opportunity” (see note 2 above); Matthias Basedau, Jonathan Fox, Jan H. Pierskalla, Georg Stuver, and Johannes Vullers, “Does Discrimination Breed Grievances—And Do Grievances Breed Violence?,” Conflict Management and Peace Science (2015): 10.1177/0738894215581329.

73. Ekkart Zimmermann, “Globalization and Terrorism,” European Journal of Political Economy 27 (2011): 156.

74. Kis-Katos et al., “On the Origin” (see note 69 above); Enders et al., “The Changing Nonlinear Relationship” (see note 8 above); Piazza, “Poverty, Minority Economic Discrimination, and Domestic Terrorism” (see note 9 above); James Piazza, “The Cost of Living and Terror: Does Consumer Price Volatility Fuel Terrorism?” Southern Economic Journal 79, no. 4 (2013): 812–31.

75. Daniel Meierrieks and Thomas Gries, “Causality between Terrorism and Economic Growth,” Journal of Peace Research 50, no. 1 (2013): 91–104; Thomas Gries, Tim Krieger, and Daniel Meierrieks, “Causal Linkages between Domestic Terrorism and Economic Growth,” Defense and Peace Economics 22, no. 5 (2009): 493–508.

76. Blomberg et al., “An Economic Model” (see note 17 above), 25.

77. Matthias Basedau and Jann Lay, “Resource Curse or Rentier Peace? The Ambiguous Effects of Oil Wealth and Oil Dependence on Violent Conflict,” Journal of Peace Research 46, no. 6 (2009): 757–76; Benjamin Smith, “Oil Wealth and Regime Survival in the Developing World, 1960–1999,” American Journal of Political Science 48, no. 2 (2004): 232–46; Terry Karl, The Paradox of Plenty: Oil Booms and Petro-States (Berkeley, CA: University of California Press, 1997).

78. Kis-Katos et al., “On the Origin” (see note 69 above).

79. Zimmermann, “Globalization and Terrorism” (see note 73 above), 156.

80. Kis-Katos et al., “On the Origin” (see note 69 above).

81. Data on ethnic polarization is not available for all countries. Countries included are listed in Table 1 in Appendix A.

82. Li, “Does Democracy Promote or Reduce” (see note 34 above).

83. National Consortium for the Study of Terrorism and Responses to Terrorism (START), “Global Terrorism Database” (2014 data file), http://www.start.umd.edu/gtd

84. Enders et al., “Domestic versus Transnational Terrorism” (see note 9 above). Joseph K. Young and Laura Dugan, “Veto players and terror,” Journal of Peace Research 48, no. 1 (2011): 19–33 operationalized attacks as foreign (transnational) and homegrown (domestic) based on the perpetrators country of origin and target.

85. Alesina et al., “Fractionalization” (see note 6 above); Daniel Posner, “Measuring Ethnic Fractionalization in Africa,” American Journal of Political Science 48, no. 4 (2004): 849–63.

86. Montalvo and Reynal-Querol, “Polarization” (see note 7 above); Reynal-Querol, “Ethnicity, Political Systems” (see note 7 above); Ellingsen, “Colorful Community” (see note 42 above).

87. We extend Montalvo and Reynal-Querol data to 2012.

88. Montalvo and Reynal-Querol, “Polarization” (see note 7 above), 798.

89. Ibid. See also Reynal-Querol, “Ethnicity, Political Systems” (see note 7 above) for a discussion of the RQ index; Esteban and Schneider, “Polarization and Conflict” (see note 25 above).

90. Enders et al., “The Changing Nonlinear Relationship” (see note 8 above); Kis-Katos et al., “On the Origin” (see note 69 above).

91. World Bank, “World Development Indicators” (Washington, DC, 2014), http://data.worldbank.org/data-catalog/world-development-indicators

92. Fearon and Laitin, “Ethnicity, Insurgency, and Civil War” (see note 3 above); Montalvo and Reynal-Querol, “Polarization” (see note 7 above); Paul Collier and Anke Hoeffler, “On the Incidence of Civil War in Africa,” Journal of Conflict Resolution 46, no. 13 (2002): 13–28.

93. See Khusrav Gaibulloev, “Terrorist Group Location Decision,” Oxford Economic Papers (2015): 21–41.

94. Lai, “Draining the Swamp” (see note 37 above); Li and Schaub, “Economic Globalization” (see note 34 above); Piazza, “Rooted in Poverty” (see note 23 above); James Piazza, “Repression and Terrorism: A Cross-National Empirical Analysis of Types of Repression and Domestic Terrorism,” Terrorism and Political Violence (2015), doi:10.1080/09546553.2014.994061

95. Randall Blimes, “The Indirect Effect of Ethnic Heterogeneity on the Likelihood of Civil War Onset,” Journal of Conflict Resolution 50, no. 4 (2006): 536–47, 538.

96. Crenshaw, “Causes of Terrorism” (see note 1 above), 384.

97. See Abdelaziz Testas, “Determinants of Terrorism in the Muslim World,” Terrorism and Political Violence 16, no. 2 (2004): 253–73; Piazza, “Rooted in Poverty” (see note 23 above); Piazza, “Repression and Terrorism” (see note 94 above).

98. Edward Muller and Erich Weede, “Cross-national Variation in Political Violence: A Rational Action Approach,” Journal of Conflict Resolution 34, no. 4 (1990): 624–51; Eric Bleich, Carolina Caeiro, and Sarah Luehrman, “State Responses to “Ethnic Riots’ in Liberal Democracies,” European Political Science Review 2 (2010): 269–95.

99. Christian Davenport, “State Repression and Political Order,” Annual Review of Political Science (2007): 10.

100. Byman, “The Logic of Ethnic Terrorism” (see note 1 above).

101. Testas, “Determinants of Terrorism” (see note 97 above); Lai, “Draining the Swamp” (see note 37 above); William Eubank and Leonard Weinberg, “Does Democracy Encourage Terrorism?,” Terrorism and Political Violence 6, no. 4 (1994): 417–35.

102. Grigore Pop-Eleches and Graeme Robertson, “Information, Elections and Political Change,” Comparative Politics 47, no. 4 (2015): 459–78.

103. Orlandrew Danzell, “Political Parties: When Do They Turn to Terror?,” Journal of Conflict Resolution 55, no. 1 (2011): 85–105; Li and Schaub, “Economic Globalization” (see note 34 above).

104. James Piazza, “Oil and Terrorism: An Investigation of Mediators,” Public Choice (2016): doi:10.1007/s11127-016–0357-0, 15

105. Jacqueline DeMeritt and Joseph K. Young, “A Political Economy of Human Rights: Oil, Natural Gas, and State Incentives to Repress,” Conflict Management and Peace Science 30, no. 2 (2013): 99–120; Courtenay Conrad and Jacqueline DeMeritt, “Constrained by the Bank and the Ballot: Unearned Revenue, Democracy, and State Incentives to Repress,” Journal of Peace Research 50, no. 1 (2012): 105–119; Alastair Smith, “The Perils of Unearned Income,” Journal of Politics 70, no. 3 (2008): 780–93.

106. Philippe LeBillion and Fouad El Khatib, “From Free Oil to ‘Freedom Oil,’” Geopolitics 9, no. 1 (2004): 109–37, 112.

107. Collier and Hoeffler, “On the Incidence” (see note 92 above); Ana Bela Santos Bravo and Carlos Mauel Mendes Dias, “An Empirical Analysis of Terrorism: Deprivation, Islamism, and Geopolitical Factors,” Defence and Peace Economics 17, no. 2 (2006): 329–41; Brock Blomberg, Nzinga H. Broussard, and Gregory D. Hess, “New Wine in Old Wineskins? Growth, Terrorism and the Resource Curse in Sub-Saharan Africa,” European Journal of Political Economy 27 (2011): 50–63; Joan Esteban, Laura Mayoral, and Debraj Ray, “Ethnicity and Conflict,” American Economic Review 102, no. 4 (2012): 1310–42; Aderoju Oyefusi, “Oil, Youths, and Civil Unrest in Nigeria’s Delta,” Conflict Management and Peace Science 27, no. 4 (2010): 326–46.

108. Sarah Brockhoff, Tim Krieger, and Daniel Meierrieks, “Great Expectations and Hard Times: The (Nontrivial) Impact of Education on Domestic Terrorism,” Journal of Conflict Resolution 59, no. 7 (2015): 1186–1215; Berrebi, “Evidence about the Link” (see note 38 above).

109. Basedau et al., “Does Discrimination Breed Grievances” (see note 72 above).

110. David Barrett, George Kurian, and Todd Johnson, World Christian Encyclopedia (Oxford, UK: Oxford Press, 2001).

111. The unit of elevation is kilometer/100.

112. See Fearon and Laitin, “Ethnicity, Insurgency, and Civil War” (see note 3 above); Cullen Hendrix, “Head for the Hills? Rough Terrain, State Capacity, and Civil War Onset,” Civil Wars 13, no. 4 (2011): 345–70.

113. Gaibulloev, “Terrorist Group Location” (see note 93 above); Cristiana Brafman Kittner, “The Role of Safe Havens in Islamist Terrorism,” Terrorism and Political Violence 19, no. 3 (2007): 307–29.

114. Examples mentioning use of rough/mountainous terrain U.S. State Department, “Country Reports on Terrorism 2015: Terrorist Safe Havens,” http://www.state.gov/j/ct/rls/crt/2015/257522.htm

115. Kittner, “The Role of Safe Havens” (see note 113 above), 307.

116. Stephen Nemeth, Jacob Mauselin, and Craig Stapley, “The Primacy of the Local: Identifying Terrorist Hot Spots Using Geographic Information Systems,” Journal of Politics 76, no. 2 (2014): 304–17.

117. Since ethnic polarization is a time-invariant variable, the fixed-effect estimation is inappropriate because it creates multicollinearity among regressors.

118. Based on test of fit, Poisson models were not appropriate, reflected in the alpha and skewness of the sample which illustrated significant over-dispersion. A. Colin Cameron and Pravin K. Trivedi, Regression Analysis of Count Data (Cambridge, UK: Cambridge University Press, 1998); Scott Long and Jeremy Freese, Regression Models for Categorical Dependent Variables Using Stata (College Station, TX: Stata Press, 2003).

119. Repression is not lagged because it is designed to capture the period of times under a given regime type. See Lai, “Draining the Swamp” (see note 37 above).

120. Lai, “Draining the Swamp” (see note 37 above); Brockhoff et al., “Great Expectations” (see note 108 above).

121. In addition to coefficient estimates and standard errors, we provide incident rate ratios (IRR) for intuitive interpretation of the statistical results. Unlike some statistical models (e.g., linear OLS or logistic and probit binary regression) where marginal effects are computable and provide a clear illustration of the magnitudes and directions of the contribution from regressors on the dependent variable, it is statistically impossible to produce marginal effects for count models (e.g., Poisson or NBREG). Instead, IRR are applied to provide similar interpretations as marginal effects. IRR represents the likelihood of dependent variable when a specific independent variable is present.

122. Badi Baltagi, Econometric Analysis of Panel Data, 5th ed. (Chichester, UK: Wiley, 2013); Jerry Hausman and William Taylor, “Panel Data and Unobservable Individual Effects,” Econometrica, 49, no. 6 (1981).

123. Blomberg et al., “Macroeconomic Consequences” (see note 12 above).

124. Enders et al., “The Changing Nonlinear Relationship” (see note 8 above); David Rapoport, “The Four Waves of Modern Terrorism,” in Attacking Terrorism, Audrey Cronin and James Ludes, eds. (Washington, D.C.: Georgetown University Press, 2004), 46–73.

125. Alesina et al., “Fractionalization” (see note 6 above).

126. Democracy is dichotomized as 1 if polity scores 6 or above, and 0 otherwise.

127. Aksoy and Carter, “Electoral Institutions” (see note 47 above).

128. Fearon and Laitin, “Ethnicity, Insurgency, Civil War” (see note 3 above).

129. Basuchoudhary and Shughart, “On Ethnic Conflict” (see note 21 above).

130. Horowitz, Ethnic Groups (see note 2 above); Montalvo and Reynal-Querol, “Polarization” (see note 7 above).

Additional information

Notes on contributors

Orlandrew E. Danzell

Orlandrew E. Danzell is an Assistant Professor in the Department of Intelligence Studies, within the Ridge College at Mercyhurst University, PA. Yao-Yuan Yeh is a Visiting Assistant Professor in the Center for International Studies at University of St. Thomas, TX. Melia Pfannenstiel is an Instructor and Researcher in the Department of Political Science at Kansas State University, KS.