¹ Hoffman, Bruce, Inside Terrorism: Revised and Expanded Edition (New York: Columbia University Press, 2006)Google Scholar

² Marcus, Aliza, Blood and Belief: The PKK and the Kurdish Fight for Independence (New York: New York University Press, 2007)Google Scholar

³ Powell, G. Bingham, Elections as Instruments of Democracy: Majoritarian and Proportional Visions (New Haven, Conn.: Yale University Press, 2000)Google Scholar

⁴ Powell, G. Bingham, Contemporary Democracies: Participation, Stability and Violence (Washington, DC: Congressional Quarterly Press, 1982)CrossRefGoogle Scholar

Krain, Matthew, ‘Contemporary Democracies Revisited: Democracy, Political Violence, and Event Count Models’, Comparative Political Studies, 31 (1998), 139–64 CrossRefGoogle Scholar

Cohen, Frank S., ‘Proportional Versus Majoritarian Ethnic Conflict Management in Democracies’, Comparative Political Studies, 30 (1997), 607–30 CrossRefGoogle Scholar

Saideman, Stephen M. et al., ‘Democratization, Political Institutions, and Ethnic Conflict: A Pooled, Cross-Sectional Time Series Analysis from 1985–1998’, Comparative Political Studies, 35 (2002), 103–29 CrossRefGoogle Scholar

⁵ Lijphart, Arend, Democracy in Plural Societies: A Comparative Exploration (New Haven, Conn.: Yale University Press, 1977)Google Scholar

⁶ Hürriyet Daily News, 25 July 2010, http://www.hurriyetdailynews.com.

⁷ Li, Quan, ‘Does Democracy Promote or Reduce Transnational Terrorist Incidents?’, Journal of Conflict Resolution, 49 (2005), 278–97 CrossRefGoogle Scholar

⁸ Eubank, William L. and Weinberg, Leonard, ‘Does Democracy Encourage Terrorism’, Terrorism and Political Violence, 6 (1994), 417–43 CrossRefGoogle Scholar

Weinberg, Leonard B. and Eubank, William L., ‘Democracy and Terrorism: What Recent Events Disclose’, Terrorism and Political Violence, 10 (1998), 108–18 CrossRefGoogle Scholar

Eubank, William L. and Weinberg, Leonard, ‘Terrorism and Democracy: Perpetrators and Victims’, Terrorism and Political Violence, 13 (2001), 155–64 CrossRefGoogle Scholar

Pape, Robert A., ‘The Strategic Logic of Suicide Terrorism’, American Political Science Review, 97 (2003), 343–61 CrossRefGoogle Scholar

Li, Quan and Schaub, Drew, ‘Economic Globalization and Transnational Terrorist Incidents: A Pooled Time Series Analysis’, Journal of Conflict Resolution, 48 (2004), 230–58 CrossRefGoogle Scholar

⁹ Li, ‘Does Democracy Promote or Reduce Transnational Terrorist Incidents?’.

¹⁰ Piazza, James, ‘A Supply-Side View of Suicide Terrorism: A Cross-National Study’, Journal of Politics, 70(1) (2008), 28–39CrossRefGoogle Scholar

Enders, Walter and Sandler, Todd, ‘Transnational Terrorism in the Post-Cold War Era’, International Studies Quarterly, 43 (1999), 145–67 CrossRefGoogle Scholar

Enders, Walter and Sandler, Todd, ‘Is Transnational Terrorism Becoming More Threatening? A Time-Series Investigation’, Journal of Conflict Resolution, 44 (2000), 307–32 CrossRefGoogle Scholar

Clauset, AaronYoung, Maxwell and Gleditsch, Kristian S., ‘On the Frequency of Severe Terrorist Events’, The Journal of Conflict Resolution, 51 (2007), 58–87 CrossRefGoogle Scholar

¹¹ Jones, Seth G. and Libicki, Martin C., How Terrorist Groups End: Lessons for Countering al Qaeda (Washington, DC: RAND Corporation, 2006)Google Scholar

¹² Engene, Jan Oskar, Terrorism in Western Europe: Explaining the Trends Since 1950 (Cheltenham, UK: Edward Elgar, 2004)Google Scholar

¹³ Deniz Aksoy, David B. Carter and Joseph Wright (2012) for evidence that non-democracies with active opposition parties experience levels of terrorism that rival what democracies experienceGoogle Scholar

Aksoy, Deniz, Carter, David B., and Wright, Joseph, ‘Terrorism in Dictatorships', Journal of Politics, 74(3) (2012), 810–826CrossRefGoogle Scholar

¹⁴ Eubank and Weinberg, ‘Does Democracy Encourage Terrorism’; Weinberg and Eubank ‘Democracy and Terrorism: What Recent Events Disclose’; Eubank and Weinberg, ‘Terrorism and Democracy: Perpetrators and Victims’; Pape, ‘The Strategic Logic of Suicide Terrorism’; Li and Schaub, ‘Economic Globalization and Transnational Terrorist Incidents: A Pooled Time Series Analysis’.

¹⁵ Schmid, Alex, ‘Terrorism and Democracy’, Terrorism and Political Violence, 4 (1992), 14–25 CrossRefGoogle Scholar

Eyerman, Joel, ‘Terrorism and Democratic States: Soft Targets or Accessible Systems’, International Interactions, 24 (1992), 151–70 Google Scholar

¹⁶ Schmid, ‘Terrorism and Democracy’; Pape, ‘The Strategic Logic of Suicide Terrorism’; Li, ‘Does Democracy Promote or Reduce Transnational Terrorist Incidents?’.

¹⁷ Erica Chenoweth, ‘Democratic Competition and Terrorist Activity’, Journal of Politics, 72(1) (2010); Joseph K. Young and Laura Dugan, ‘Veto Players and Terror’, Journal of Peace Research, 48 (2011), 19–33.

¹⁸ James A. Piazza, ‘Terrorism and Party Systems in the States of India’, Security Studies, 19 (2010), 99–123.

¹⁹ Lijphart, Democracy in Plural Societies: A Comparative Exploration; Powell, Contemporary Democracies: Participation, Stability and Violence; Krain, ‘Contemporary Democracies Revisited: Democracy, Political Violence, and Event Count Models’; Cohen, ‘Proportional Versus Majoritarian Ethnic Conflict Management in Democracies’; Saideman et al., ‘Democratization, Political Institutions, and Ethnic Conflict: A Pooled, Cross-Sectional Time Series Analysis from 1985–1998’.

²⁰ Powell, Contemporary Democracies: Participation, Stability and Violence, p. 72.

²¹ Krain, ‘Contemporary Democracies Revisited: Democracy, Political Violence, and Event Count Models’; Cohen, ‘Proportional Versus Majoritarian Ethnic Conflict Management in Democracies’; Saideman et al., ‘Democratization, Political Institutions, and Ethnic Conflict: A Pooled, Cross-Sectional Time Series Analysis from 1985–1998’; Marta Reynal-Querol, ‘Ethnicity, Political Systems, and Civil Wars’, Journal of Conflict Resolution, 46 (2002) 29–54.

²² Lijphart, Democracy in Plural Societies: A Comparative Exploration.

²³ Li, ‘Does Democracy Promote or Reduce Transnational Terrorist Incidents?’; Dennis Foster, Alex Braithwaite & David Sobek, ‘There Can Be No Compromise: Institutional Inclusiveness, Fractionalization, and Domestic Terrorism’, 2013 (forthcoming at British Journal of Political Science).

²⁴ Weinberg, LeonardPedahzur, Ami and Perlinger, Arie, Political Parties and Terrorist Groups (New York: Routledge, 2009)Google Scholar

²⁵ Harmel, Robert and Robertson, John D., ‘Formation and Success of New Parties: A Cross-National Analysis’, International Political Science Review, 6 (1985), 501–23 CrossRefGoogle Scholar

Robert Jackman and Karin Volpert ‘Conditions Favoring Parties of the Extreme Right in Western Europe’, British Journal of Political Science, 26 (1996), 501–21CrossRefGoogle Scholar

Willey, Joseph, ‘Institutional Arrangements and the Success of New Parties in Old Democracies’, Political Studies, 46 (1998), 651–68 CrossRefGoogle Scholar

Arzheimer, Kai and Carter, Elizabeth, ‘Political Opportunity Structures and Right-wing Extremist Party Success’, European Journal of Political Research, 45 (2006), 419–43 CrossRefGoogle Scholar

Abedi, Amir, ‘Challenges to Established Parties: The Effects of Party System Features on the Electoral Fortunes of Anti-political-establishment Parties’, European Journal of Political Research, 41 (2002), 551–83 CrossRefGoogle Scholar

²⁶ Discontented groups can be marginalized along a variety of social and political cleavages. For instance, some groups are marginalized relative to their ethnic attachment (for example, Kurds in Turkey), while others are marginalized relative to their political ideology (such as leftists in Germany).

²⁷ Mesquita, Ethan Bueno de, ‘Terrorist Factions’, Quarterly Journal of Political Science, 3 (2008), 399–418 Google Scholar

²⁸ There has been some variation in the permissiveness of France's electoral system; however, it has generally been relatively unpermissive and has always been much more restrictive than that of the Netherlands.

²⁹ In fact, the only election in which the FN sent delegates to the Assembly was in 1986, after Mitterrand changed the electoral system to party-list proportional. The change was undone two years later, and the FN lost its seats in the next legislative election.

³⁰ A somewhat similar distinction is made between ‘anti-establishment’ and ‘establishment’ parties in the literature on extremist political parties (see Abedi, ‘Challenges to Established Parties: The Effects of Party System Features on the Electoral Fortunes of Anti-political-establishment Parties’). However, we argue that an `anti-establishment' party like the FN in France is not the same in terms of extremity as an anti-system terrorist group. Simply put, the FN works within the existing political system and has goals that, although extreme, do not call for a complete overhaul of the French political system.

³¹ Hypothesis 1a is technically more difficult to confirm than Hypothesis 1b, as Hypothesis 1b is the null hypothesis that electoral permissiveness has no significant effect on anti-system group emergence. However, for our arguments to be sound, both components of the hypothesis should be confirmed. Namely, permissive electoral institutions should reduce the propensity of within-system groups to emerge and have no significant effect on anti-system groups.

³² Jones and Libicki, How Terrorist Groups End: Lessons for Countering al Qaeda.

³³ Engene, Terrorism in Western Europe: Explaining the Trends Since 1950.

³⁴ In theory, group emergence could be broken down by month. However, we do not have systematic data that accurately attributes the emergence of groups to a particular month. Furthermore, the structure of all existing data that we will use in our analysis makes the year the natural unit of analysis.

³⁵ Cheibub, JoséGandhi, Jennifer and Vreeland, James, ‘Democracy and Dictatorship Revisited’, Public Choice, 143(1) (2010), 67–101CrossRefGoogle Scholar

³⁶ Jones and Libicki, How Terrorist Groups End: Lessons for Countering al Qaeda; Engene, Terrorism in Western Europe: Explaining the Trends Since 1950.

³⁷ None of the key results is affected if we do not treat territorial change groups as anti-system.

³⁸ The GTD is maintained by START and is available at http://www.start.umd.edu/gtd/.

³⁹ None of the results reported below change substantively if we exclude groups that have the goal of empire.

⁴⁰ Cheibub, Gandhi and Vreeland, ‘Democracy and Dictatorship Revisited’.

⁴¹ Regan, Patrick M.Frank, Richard W. and Clark, David H., ‘New Datasets on Political Institutions and Elections, 1972–2005’, Conflict Management and Peace Science, 26 (2009), 286–304 CrossRefGoogle Scholar

⁴² Golder, Matt, ‘Democratic Electoral Systems Around the World, 1946–2000’, Electoral Studies, 24 (2005), 103–21 CrossRefGoogle Scholar

⁴³ Vreeland, James, ‘The Effect of Political Regime on Civil War Unpacking Anocracy’, The Journal of Conflict Resolution, 52(3) (2008), 401–25CrossRefGoogle Scholar

⁴⁴ Rae, Douglas, The Political Consequences of Electoral Laws (New Haven, Conn.: Yale University Press, 1967)Google Scholar

Lijphart, Arend, Electoral Systems and Party Systems (New York: Oxford University Press, 1994)CrossRefGoogle Scholar

Lijphart, Arend, Patterns of Democracy: Government Forms and Performance in Thirty-Six Countries (New Haven, Conn.: Yale University Press, 1999)Google Scholar

⁴⁵ Monroe, Burt L., ‘Understanding Electoral Systems: Beyond Plurality versus PR’, PS: Political Science and Politics, 27 (1994), 667–82 Google Scholar

⁴⁶ Duverger, Maurice, Political Parties: Their Organization and Activity in the Modern State (New York: John Wiley, 1963)Google Scholar

Cox, Gary W., Making Votes Count: Strategic Coordination in the World's Electoral Systems (Cambridge: Cambridge University Press, 1997)CrossRefGoogle Scholar

⁴⁷ Lijphart, Electoral Systems and Party Systems; Octavio Amorim Neto and Gary W. Cox, ‘Electoral Institutions, Cleavage Structures, and the Number of Parties’, American Journal of Political Science, 41 (1997), 149–74; Golder, ‘Democratic Electoral Systems Around the World, 1946–2000’; Thomas Brambor, William Roberts Clark and Matt Golder, ‘Are African Party Systems Different?’, Electoral Studies, 26 (2006), 315–23.

⁴⁸ An alternative is to use average district magnitude rather than the median. However, Neto and Cox warn against using simple average of district magnitude, since in the process of averaging each district counts equally regardless of its population (Neto and Cox, ‘Electoral Institutions, Cleavage Structures, and the Number of Parties’). That being said, the simple correlation between median and average district magnitude measures in our data is 0.99. Unsurprisingly, when we estimate all of our models with average district magnitude, all of our results are robust.

⁴⁹ For example, an increase in district magnitude from 2 to 3 will have more influence on the representation of multiple parties than an increase from 100 to 101. Rein Taagepera and Bernard Grofman, ‘Rethinking Duverger's Law: Predicting the Effective Number of Parties in Plurality and PR Systems–Parties Minus Issues Equals One’, European Journal of Political Research, 13 (1985), 341–52. Neto and Cox. ‘Electoral Institutions, Cleavage Structures, and the Number of Parties’; Golder, ‘Democratic Electoral Systems Around the World, 1946–2000’; Brambor, Clark and Golder, ‘Are African Party Systems Different?’.

⁵⁰ Fearon, James D. and Laitin, David D., ‘Ethnicity, Insurgency, and Civil War’, The American Political Science Review, 97 (2003), 75–90 CrossRefGoogle Scholar

⁵¹ Regan, Frank and Clark, ‘New Datasets on Political Institutions and Elections, 1972–2005’Google Scholar

⁵² Fearon and Laitin, ‘Ethnicity, Insurgency, and Civil War’.

⁵³ We also tried including the logged percentage of mountains in the target country, which Fearon and Laitin found to be an important determinant of civil war. Inclusion or exclusion of this variable has no effect on the results, so we do not include it.

⁵⁴ William F. Shugart, ‘An Analytical History of Terrorism’, Public Choice, 128 (2006), 7–39.

⁵⁵ Chenoweth, ‘Democratic Competition and Terrorist Activity’.

⁵⁶ Beck, NathanielKatz, Jonathan N. and Tucker, Richard, ‘Taking Time Seriously: Time-Series-Cross-Section Analysis with a Binary Dependent Variable’, American Journal of Political Science, 42 (1998) 1260–88Google Scholar

Carter, David B. and Signorino, Curtis S., ‘Back to the Future: Modeling Temporal Dependence in Binary Data’, Political Analysis, 18 (2010), 271–92 CrossRefGoogle Scholar

⁵⁷ Cheibub, Gandhi and Vreeland, ‘Democracy and Dictatorship Revisited’.

⁵⁸ We also estimate the models of anti-system and within-system group emergence simultaneously, using a bivariate probit model that allows their error terms to be correlated. The results are very similar to those reported in Tables 4 and 5.

⁵⁹ It has been suggested to us that there is significant temporal variations in the kinds of groups that are included in this data, although neither simple tabulations of the data nor examination of trends in the statistical models provide any evidence of this. We include year-fixed effects to appease readers who have this concern. Inclusion or exclusion of year-fixed effects has no influence on any of our key results.

⁶⁰ We also ran a model for the emergence of groups that Engene was not able to classify in terms of their goals. The results are essentially the same as in the pooled groups equations.

⁶¹ Furthermore, this finding does not survive country-specific effects. Below, we show that the within-system group findings survive this robustness check.

⁶² To assess sensitivity to potentially influential cases, we dropped each of the six countries with the highest district magnitudes and each of the six with the lowest district magnitudes to see if the results remain robust. Specifically, we removed the Netherlands, Israel, Brazil, Austria, Italy and Portugal, all of which had very high district magnitudes across many years, and the UK, the United States, Canada, France, Germany (West Germany pre-1990), India and Australia, which all had district magnitudes of 1 for several years. The results remained statistically significant in all cases in which we dropped one of these cases.

⁶³ Note that the difference in the number of observations in the tables is due to variations in the data on district magnitude in terms of countries and years. Also, the models that analyse the TWEED data have relatively few observations, as only sixteen West European countries are included in the analysis.

⁶⁴ As a robustness check, we ran individual models for each of the six primary goals in the Jones and Libicki data and the four goals in the Engene data. Unsurprisingly, in the Jones and Libicki data, the within-system results are largely driven by groups with the goal of policy change, since these groups are the most numerous. The results for the anti-system goals in the Jones and Libicki data are consistent with expectations. The results for the individual group goal regressions using TWEED data are also quite consistent with our expectations. The results for the two anti-system goals, separatist and irredentist, mirror the results shown in Table 5. The within-system group results in the TWEED data are driven by the state defence groups, as there are 102 such groups and only eighteen autonomist groups.

⁶⁵ Note that we do not include the participation variable or the federal system variable in the TWEED models, as we lose about twenty years of data by doing so. As in Table 4, the key results are unaffected by inclusion of these variables.

⁶⁶ Li, ‘Does Democracy Promote or Reduce Transnational Terrorist Incidents?’.

⁶⁷ Li, ‘Does Democracy Promote or Reduce Transnational Terrorist Incidents?’.

⁶⁸ None of the results for the anti-system group models, or models that pool all groups, differ from those reported above. Thus, to save space we only include the within-system group models.

⁶⁹ Schmid, ‘Terrorism and Democracy’; Eubank and Weinberg, ‘Does Democracy Encourage Terrorism’; Weinberg and Eubank, ‘Democracy and Terrorism: What Recent Events Disclose’; Eyerman, ‘Terrorism and Democratic States: Soft Targets or Accessible Systems’; Eubank and Weinberg, ‘Terrorism and Democracy: Perpetrators and Victims’; Pape, ‘The Strategic Logic of Suicide Terrorism’; Li, ‘Does Democracy Promote or Reduce Transnational Terrorist Incidents?’; Chenoweth, ‘Democratic Competition and Terrorist Activity’.