Population is the main driver of war group size and conflict casualties

Rahul C. Oka, Marc Kissel, Mark Golitko, Susan Guise Sheridan, Nam C. Kim, Agustín Fuentes

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The proportions of individuals involved in intergroup coalitional conflict, measured by war group size (W), conflict casualties (C), and overall group conflict deaths (G), have declined with respect to growing populations, implying that states are less violent than smallscale societies. We argue that these trends are better explained by scaling laws shared by both past and contemporary societies regardless of social organization, where group population (P) directly determines W and indirectly determines C and G. W is shown to be a power law function of P with scaling exponent X [demographic conflict investment (DCI)]. C is shown to be a power lawfunction ofW with scaling exponent Y [conflict lethality (CL)]. G is shown to be a power law function of P with scaling exponent Z [group conflict mortality (GCM)]. Results show that, while W/P and G/P decrease as expected with increasing P, C/W increases with growing W. Small-scale societies show higher but more variance in DCI and CL than contemporary states. We find no significant differences in DCI or CL between small-scale societies and contemporary states undergoing drafts or conflict, after accounting for variance and scale. We calculate relative measures of DCI and CL applicable to all societies that can be tracked over time for one or multiple actors. In light of the recent global emergence of populist, nationalist, and sectarian violence, our comparison-focused approach to DCI and CL will enable better models and analysis of the landscapes of violence in the 21st century.

Original languageEnglish (US)
Pages (from-to)E11101-E11110
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number52
StatePublished - Dec 26 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General


  • Conflict casualties
  • Conflict investment
  • Conflict lethalit
  • Population scaling
  • War group size


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