1. Diffusion of Homicides from Illegal Firearm Markets Jeffrey FaganGarth Davies Columbia UniversitySimon Fraser University

2. This Research Extension of theory and research on social contagion to the case of gun violence and gun markets Identify epidemic patterns Isolate effects of gun markets as sources of “pathogen” that both weakens host susceptibility and directly increases disease risk – in this case, gun violence Locate highest risk areas

3. Social Contagion Diffusion: the spread of abstract ideas and concepts, technical information, and practices within a social system The S-Curve revised (Godin, Rogers)

4. Examples of Social Contagion Diffusion of Innovation Corn Seed Experiments (Ryan and Neal) ­ Adaptation of Tetracyclene (Coleman, Burt) Consumer Behavior and Cultural Adaptations (Gladwell) ­ Fashion, Music Political Thought Language Problem behaviors (Rowe and Rogers) ­ Teenage Pregnancy, Smoking, Drug and Alcohol Use ­ School Dropout ­ Suicide Lynchings (Tolnay, 1998) Riots (Short) Gang homicides (Papachristos, 2005)

5. Mechanisms of Social Contagion Network interactions (Burt, Kandel)  egos interact at points of contact between innovator and adaptor  homogeneity and density of social networks dictates patterns of contact and social interaction (homophily)  Information obtained from close peers located in social and organizational networks has more weight than information obtained from objective sources Cultural software (Balkin)  memetics within social networks: spread of beliefs and ideas via competition of ideas and survival of fittest, social norms transmission Behavioral scripts (Fagan and Wilkinson, Nisbitt)  Practice and reinforcement of contingent behavioral responses Infectious disease model of contagion Most work on individuals and social networks, with attention to social context as facilitating transmission within networks,  Less on contagion across social areas  Lynching, Homicide research – across larger aggregates

6. Illicit Gun Markets and Violence Recent evidence  Braga and Pierce (2005) – disrupting gun markets reduces gun availability But generally little research on firearm violence epidemiology and proximity to sources of illegal guns  Some qualitative evidence using small areas to approximate local markets  Difficulties in identifying spatial and economic parameters of these markets In this research, we use localized measures of gun seizures to approximate location and intensity of illegal gun availability

7. Litigation Interest Municipal and private lawsuits Convergence of criminal and tort responsibility Theories  Public nuisance  Product liability  “Toxic tort” theory Proximal causation  risk of death following exposure to firearms Gun litigation as a privatized form of risk regulation

8. Data Sources Gun Seizures BATF Trace Data, New York City Extract, geocoded to seizure location, FOIA Extract dated February 15, 2002; Bureau of Alcohol, Tobacco and Firearms NAACP Extract dated September 13, 2002 Homicide and Assault NYC Dept of Health, Injury Surveillance System  Vital Statistics records of deaths geocoded to census tract of victim residence  SPARCS hospital admissions records for intentional injuries, geocoded to patient residence  ICD10 codes for firearm injuries Social and Economic Composition New York City Department of City Planning, PL 94-171 Redistricting File and Summary File for 1990 and 200 U.S. Census, tracts reconciled to 1990 boundaries

14. Figures 1 and 2. Gun Seizures and Gun Homicides, New York City Census Tracts Figures 1 and 2. Gun Seizures and Gun Homicides, New York City Census Tracts 1997 and 2002

15. Analysis Estimate models of gun seizures for each year in panel, use residuals as measures of gun market intensity (lagged)  We don’t think of gun markets as a tx, which would call for a different analytic strategy Estimate spatial lag for adjacent census tracts, controlling for second-order diffusion beyond immediate diffusion area Include social structure both in estimation of gun markets and in homicide models (we use residuals of gun seizures) Models estimated using mixed effects poisson regressions with AR(1) covariance, random intercepts and random effects for time  See, Singer and Willett (2004), Rabe-Hesketh, S., Skrondal, A. and Pickles, A. (2005)

16. Violence Gun MarketFactors Violence Gun MarketFactors Tract Neighborhood Second Order Neighborhood 1.1.

24. Conclusions Evidence of contagious effects from illegal gun markets, as measured by gun seizures, on gun homicide and total homicide  Weaker evidence for assaults Effects concentrated at extremes of gun markets and at concentrations of “susceptibility” Assaults are more heterogeneous, not closely linked to of gun markets Quarantine v. Innoculation  Policies to disrupt gun markets should have payoffs  Distributive justice perspective points to innoculation as preferable strategy (Markovits, 2005)