Is Gun Violence Contagious? A Spatiotemporal Test
Existing theories of gun violence predict stable spatial concentrations and contagious diffusion of gun violence into surrounding areas. Recent empirical studies have reported confirmatory evidence of such spatiotemporal diffusion of gun violence. However, existing space/time interaction tests cannot readily distinguish spatiotemporal clustering from spatiotemporal diffusion. This leaves as an open question whether gun violence actually is contagious or merely clusters in space and time. Compounding this problem, gun violence is subject to considerable measurement error with many nonfatal shootings going unreported to police.
Using point process data from an acoustical gunshot locator system and a combination of Bayesian spatiotemporal point process modeling and classical space/time interaction tests, this paper distinguishes between clustered but non-diffusing gun violence and clustered gun violence resulting from diffusion.
This paper demonstrates that contemporary urban gun violence in a metropolitan city does diffuse in space and time, but only slightly.
These results suggest that a disease model for the spread of gun violence in space and time may not be a good fit for most of the geographically stable and temporally stochastic process observed. And that existing space/time tests may not be adequate tests for spatiotemporal gun violence diffusion models.
KeywordsGun violence Contagion Spatiotemporal methods
SRF was supported by ERC (FP7/617071) and EPSRC (EP/K009362/1). The authors thank Richerd Berk, Shawn Bushway, John MacDonald, Theresa Smith, George Tita, and three anonymous reviewers for helpful comments on this manuscript.
- Chicago Police Department (2012) 2011 Chicago Murder Analysis. Technical report, City of Chicago, Chicago, ILGoogle Scholar
- Cressie N, Wikle C (2011) Statistics for spatio-temporal data. Wiley, HobokenGoogle Scholar
- de Tarde G (1903) The laws of imitation. H. Holt and Company, New YorkGoogle Scholar
- Gelman A, Jakulin A, Pittau MG, Su Y-S (2008) ‘A weakly informative default prior distribution for logistic and other regression models’. The Ann Appl Stat, 360–1383.Google Scholar
- Knox EG (1964a) The detection of space-time interactions. J Royal Stat Soc Ser C (Appl Stat) 13(1):25–29Google Scholar
- Knox G (1964b) Epidemiology of childhood leukaemia in northumberland and Durham. Br J Prevent Soc Med 18(1):17–24Google Scholar
- Loftin C (1986) Assaultive violence as a contagious social process. Bull N Y Acad Med 62(5):550–555Google Scholar
- Mantel N (1967) The detection of disease clustering and a generalized regression approach. Cancer Res 27(2 Part 1):209–220Google Scholar
- Metropolitan Police Department (2006) A Report on Juvenile and Adult Homicide in the Distict of Columbia. Technical report, Metropolitan Police Department, Research and Resource Development Department, Washington, D.CGoogle Scholar
- Patel DM, Simon MA, Taylor RM (2012) Contagion of violence–workshop summary, technical report. Institute of Medicine and National Research Council of the National Academies, WashingtonGoogle Scholar
- Petho A, Fallis DS, Keating D (2013) Investigations. In: Gunfire detection system captures about 39,000 shooting incidents in the District. The Washington Post. https://www.washingtonpost.com/investigations/shotspotter-detection-system-documents-39000-shooting-incidents-in-the-district/2013/11/02/055f8e9c-2ab1-11e3-8ade-a1f23cda135e_story.html
- Philadelphia Police Department (2014) Murder/Shooting Analysis 2013. Technical report, Philadelphia Police Department, Philadelphia, PAGoogle Scholar
- Ramlau-Hansen H (1983) ‘Smoothing counting process intensities by means of kernel functions’. The Ann Stat, 453–466.Google Scholar
- Reiss AJ, Roth JA, Miczek KA, National Research Council (US). Panel on the understanding and control of violent behavior (1993), understanding and preventing violence. National Academy Press-1994, Washington, DCGoogle Scholar
- Skogan W, Hartnett S, Bump N, Dubois J (2009) Evaluation of ceasefire-Chicago, technical report. US, Department of Justice, WashingtonGoogle Scholar
- Stan Development Team (2016) ‘Stan: A c++ library for probability and sampling, version 2.9.0’Google Scholar
- Tita G, Cohen J (2004) Measuring spatial diffusion of shots fired activity. In: Goodchild MF, Janelle DG (eds) Spatially integrated social science. Oxford University Press, New York, pp 171–204Google Scholar
- Tita G, Riley J, Ridgeway G, Grammich C, Abrahamse A, Greenwood P (2003) Reducing gun violence: results from an intervention in east Los Angeles. RAND Corporation, Santa MonicaGoogle Scholar
- Wooditch A, Weisburd D (2015) Using space-time analysis to evaluate criminal justice programs: an application to stop-question-frisk practices. J Quant Criminol 32(2):1–23Google Scholar