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Self-exciting point process models of civilian deaths in Iraq

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Abstract

Our goal in this article is to characterize temporal patterns of violent civilian deaths in Iraq. These patterns are expected to evolve on time-scales ranging from years to minutes as a result of changes in the security environment on equally varied time-scales. To assess the importance of multiple time-scales in evolving security threats, we develop a self-exciting point process model similar to that used in earthquake analysis. Here the rate of violent events is partitioned into a background rate and a foreground self-exciting component. Background rates are assumed to change on relatively long time-scales. Foreground self-excitation, in which events trigger an increase in the rate of violence, is assumed to be short-lived. We explore the model using data from Iraq Body Count on civilian deaths between 2003 and 2007. Our results indicate that self-excitation makes up as much as 37–50 per cent of all violent events and that self-excitation lasts at most between two and six weeks, depending upon the district in question. Appropriate security responses may benefit from taking these different time-scales of violence into consideration.

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Acknowledgements

We would like to thank Rick Schoenberg and two anonymous referees for their insights. This work was supported by ARO grants (STIR) W911NS-09-1-0559 and W911NF1010472, ARO MURI grant 50363-MA-MUR, ONR grant N000141010221 and AFOSR-MURI grant FA9550-10-1-0569.

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Authors and Affiliations

  1. Department of Mathematics, University of California – Los Angeles, 90095-1555, CA, USA

    Erik Lewis & Andrea L Bertozzi

  2. Department of Mathematics and Computer Science, Santa Clara University, 500 El Camino Real, Santa Clara, 95053-0290, CA, USA

    George Mohler

  3. Department of Anthropology, University of California, 341 Haines Hall, Box 951553, Los Angeles, 90095-1553, CA, USA

    P Jeffrey Brantingham

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  1. Erik Lewis
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  2. George Mohler
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  4. Andrea L Bertozzi
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Correspondence to P Jeffrey Brantingham.

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Lewis, E., Mohler, G., Brantingham, P. et al. Self-exciting point process models of civilian deaths in Iraq. Secur J 25, 244–264 (2012). https://doi.org/10.1057/sj.2011.21

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