Scale invariance in the 2003-2005 Iraq conflict

The number of reported social systems that apparently display power-law correlations (i.e., scale-free patterns) has increased dramatically in recent years, ranging from city growth and economics to global terrorism. Using the set of violence events in the 2003-2005 Iraq stabilization phase (i.e., from May 1, 2005), existence of scale-free patterns in event fatalities is shown. This property is also present in the tail of distributions of events divided into groups based on the type of used weapon. Lognormal distribution description was also tried, showing the superiority of the power-law function to describe the behavior of heavy tails. Time series for civilian and military fatalities were studied using the so-called detrended fluctuation analysis. Civilian fatalities showed uncorrelated behavior, implying a lack of memory effects on the evolution of daily civilian fatalities. In contrast, military fatalities displayed long-range correlated behavior.