Self-exciting point process models of civilian deaths in Iraq
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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.
Keywordsmodeling violence point process rational choice theory routine activity theory density estimation
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