Looking back on anger: Explaining the social origins of left-wing and nationalist-separatist terrorism in Western Europe, 1970-2007

A unique dataset is used to separately analyze the social origins of left-wing and nationalist-separatist terrorism in 17 Western European countries between 1970 and 2007. We argue that the differences in the historic roots, ultimate goals as well as their negotiability, levels of domestic and international support, and politico-military strategies of these types of ideologically or ethnically motivated terrorism make it plausible that they respond differently to specific social conditions and changes. We show that there are indeed factors that matter either to left-wing (e.g., the Cold War, leftist party strength) or nationalist-separatist terrorism (e.g., ethnic polarization, non-violent protest). However, both types of terrorism are robustly associated with larger populations and higher unemployment rates. This suggests that both may be ameliorated through social progress, even though ethnic terrorism seems to respond more strongly to socio-economic and political incentives (e.g., economic progress, political participation). Finally, we show that a pooling of terrorism data - which disregards motivational bonds, but is nevertheless common in empirical analyses - may mask the role of otherwise relevant terrorism correlates in distinct types of terrorism.