A central question is whether past border changes help explain today's civil wars. Departing from state-centered designs, this study shifts focus to "aggregate" ethnic groups—defined independently of state borders—and introduces a new index of "territorial fractionalization" that measures how fragmented such groups are across states.
📚 What was measured and why
- Territorial fractionalization: a new index capturing the degree to which an ethnic group’s settlement area is split across multiple states.
- Core hypothesis: higher territorial fractionalization increases the risk of civil conflict for an ethnic group.
- Additional expectation: groups that experienced increases in fragmentation (for example through postimperial border changes) are especially prone to violence, through dynamics such as irredentism and secessionist claims.
📊 How fragmentation and conflict were tested
- Combined geocoded data on ethnic settlement areas with newly collected data on international border changes dating back to 1886.
- Conducted mediation analysis using ethnonationalist claims to assess causal pathways linking fragmentation to conflict.
- Unit of analysis: aggregate ethnic groups worldwide, covering 1946–2017.
- Robustness checks: inclusion of control variables, fixed effects, and alternative historical ethnicity datasets.
🔍 Key findings
- Greater territorial fractionalization is associated with a higher risk of civil conflict for an ethnic group.
- Ethnic groups that became more fragmented over time show particularly elevated violence risk, consistent with patterns of postimperial revisionism, irredentism, and secession.
- Mediation analysis indicates that ethnonationalist claims help explain part of the link between fragmentation and conflict.
- Results hold under multiple model specifications and alternative measures of historical ethnicity.
📌 Why it matters
- Shifts attention away from state-level explanations to the cross-border spatial distribution of ethnic groups, revealing long-term consequences of border change.
- Suggests that historical border revisions can create lasting conditions for nationalist conflict, with implications for conflict prevention, minority protection, and the study of irredentism and secession.
