Berlin 2012 – scientific programme
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SOE: Fachverband Physik sozio-ökonomischer Systeme
SOE 8: Focus Session: Models of War and Conflict
SOE 8.1: Invited Talk
Tuesday, March 27, 2012, 09:30–10:00, H 0110
The distribution and dynamics of war sizes — •Aaron Clauset1,2, Lars-Erik Cederman3, and Kristian Gleditsch4,5 — 1University of Colorado, Boulder, USA — 2Santa Fe Institute, USA — 3ETH Zurich, Switzerland — 4University of Essex, UK — 5Center for the Study of Civil War, Norway
The severity of international wars over the past 200 years robustly follows a power-law distribution, a pattern first observed by L.F. Richardson in the 1940s. It remains unknown, however, what socio-political mechanisms produce this behavior, to what degree the underlying processes are non-stationary, and whether the more frequent civil wars follow fundamentally different rules.
We present a novel analysis of a worldwide database of civil war severities since World War II and show that a conflict's severity generically evolves according to a multiplicative random walk whose length is governed by a decreasing cessation probability. For civil wars, the walk's origin and limits are constrained by population, which leads to non-power-law behavior in the upper tail. When these limit is removed---analogous to an international conflict in which war spreads like a contagion---Richardson's power-law returns. A simple non-parametric model with these features alone confirms these qualitative results and robustly reproduces the large-scale statistical patterns in civil wars worldwide.