Post on 21-Jan-2016
description
Diffusion of Homicides from Illegal Firearm Markets
Jeffrey Fagan Garth DaviesColumbia University Simon Fraser University
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
Social Contagion Diffusion: the spread of abstract ideas and
concepts, technical information, and practices within a social system
The S-Curve revised (Godin, Rogers)
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)
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
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
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
Data SourcesGun 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 SystemVital Statistics records of deaths geocoded to census tract of victim residenceSPARCS hospital admissions records for intentional injuries, geocoded to patient residenceICD10 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
Figure 1 Gun and Non-Gun Homicides, New York City, 1968-2000
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NONGUN
Table 1. Homicide and Assault Counts and Rates, New York City Census Tracts, 1996-2000 1996 1997 1998 1999 2000 2001 2002
Counts
ATF Gun Seizures 822 6305 3192 2509 3033 2704 1565
Total Homicide 852 715 569 634 648 609 544
Gun Homicide 580 445 341 367 413 346 325
Total Assault 6038 5462 5384 5126 5037
Gun Assault 1081 846 806 810 789
Rates (per 100,000)
ATF Gun Seizures 11.98 97.74 50.77 40.75 40.29 54.09 27.59
Total Homicide 10.94 9.16 7.27 8.04 7.79 7.97 6.83
Gun Homicide 7.67 5.85 4.34 4.38 5.05 4.44 4.09
Total Assault 92.46 80.83 79.24 78.71 77.04
Gun Assault 14.94 12.56 12.82 11.89 10.94
Source: New York City Department of Health and Mental Hygiene, Division of Epidemiology, various years; Bureau of Alcohol, Tobacco and Firearms Trace Data, FOIA Extract dated February 15, 2002; Bureau of Alcohol, Tobacco and Firearms NAACP Extract dated September 13, 2002; New York City Department of City Planning, PL 94-171 Redistricting File and Summary File 3 (STF3a) of the 1990 and 2000 U.S. Census.
Table 2. Correlations between Gun Homicides, Gun Assaults, and Gun Seizures, by Census Tract, New York City, 1996-2000, Correlations (Pearson Correlation Coefficients, Two-Tailed Significance Test)a
ATF Gun Seizures
Total Homicides
Gun Homicides
Total Assaults
ATF Gun Seizures --
Total Homicides .715** --
Gun Homicides .690** .936** --
Total Assaults .698** .709** .666** --
Gun Assaults .669** .698** .676** .840**
Source: New York City Department of Health and Mental Hygiene, Division of Epidemiology, various years; Bureau of Alcohol, Tobacco and Firearms Trace Data, FOIA Extract dated February 15, 2002; Bureau of Alcohol, Tobacco and Firearms NAACP Extract dated September 13, 2002; New York City Department of City Planning, PL 94-171 Redistricting File and Summary File 3 (STF3a) of the 1990 U.S. Census.
Table 3. Descriptive Statistics for Injury, Fatality, and Census Tract Social and Economic Characteristics, New York City Census Tracts: 1990 Census Data
Valid N of
Census Tracts
Mean Standard Deviation
Social and Economic Characteristics
% Households with Public Assistance Income 1969 14.05 12.92
Gini Index of Income Inequality for Total Household Income 1969 0.38 0.08
% Households Under Poverty Level 1969 18.35 14.59
% High School Graduates - Total - 25+ 1971 66.20 15.78
% Employed in Managerial, Professional, or Technical Jobs 1970 29.63 14.89
% Employed Total 1970 90.25 6.49
% in Labor Force 1971 60.79 10.03
% Female Headed Households with Children < 18 years 1969 10.27 10.07
% Nonwhite 1971 55.52 36.08
Racial Fragmentation Indexa 1971 0.38 0.19
Supervision Ratio (25-64 by 5-24) 1971 0.53 0.36
%Youth Population (5-15) 1971 14.91 6.33
% Foreign Born 1971 27.66 14.88
Linguistic Isolation - % Homes with no English Speaker 1971 11.23 9.94
Residential Mobility - % Living in Same House as 1985 1971 63.50 10.16
% Occupied Units that are Rentals 1969 65.80 25.37
Total Population – 1990 1971 3691 2863
Source: New York City Department of City Planning, Summary File 3 (STF3a) of the 1990 U.S. Census.
Table 4. Factor Scores, New York City Census Tracts, 1990 and 2000
1990 2000
Variable Weight
Eigen-value
% Variance
Variable Weight
Eigen-value
% Variance
Poverty/Inequality 5.60 69.94 5.50 68.71
% Households Below Poverty Level 0.93 0.92
% Households with Public Assistance Income 0.93 0.88
% Less Than High School Graduates 25+ 0.90 0.89
Gini Index Total Household Income Inequality 0.86 0.87
% FHH w/ Children < 18 0.86 0.83
% Unemployed 0.77 0.77
% Not Employed Mang’l, Prof’l, or Tech Jobs 0.74 0.75
% Not in Labor Force 0.67 0.69
Segregation 1.29 64.59 1.17 58.39
Racial Fragmentation Indexa 0.80 0.76
% Nonwhite 0.80 0.76
Supervision 1.59 79.45 1.69 84.30
%Youth Population (5-15) 0.89 0.92
Supervision Ratio (25-64 by 5-24) 0.89 0.92
Immigration 1.54 76.89 1.56 78.08
% Homes with no English Speaker 0.88 0.88
% Foreign Born 0.88 0.88
Housing Stability 1.31 65.62 1.32 66.00
% Living in Same House as 5 Years Ago 0.81 0.81
%Occupied Units that are Rentals 0.81 0.81
Source: New York City Department of City Planning, Summary File 3 (STF3a) of the 1990 U.S. Census. a. For the computation of racial fragmentation, see: Charles Lewis Taylor & Michael C. Hudson, World Handbook of Political and Social Indicators 216 (1972). Racial fragmentation is a measure of the racial heterogeneity within an area, and is computed as: 1 - ((P)2), where P = proportion of each race within the spatial unit.
Figures 1 and 2. Gun Seizures and Gun Homicides,New York City Census Tracts
1997 and 2002
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)
Violence
Gun MarketFactors
Violence
Gun MarketFactors
Tract
Neighborhood
Second Order Neighborhood
1.
Table 5. Mixed Effects Poisson Regression of Gun Seizures by Neighborhood Social Structure, New York City Census Tracts, 1996-2002 Effect Est. t
Intercept -5.380
-23.54** Time -.080 -11.33** Population (Logged) .682 24.63** Poverty .630 13.96** Segregation .117 3.25** Social Control -.1719 -3.53** Immigration -.311 -11.35** Housing .207 5.75** Time Interactions
Poverty .005 .45 Segregation .006 .65 Social Control .018 1.63 Immigration -.019 -2.87** Housing -.020 -2.34*
-2 Log Likelihood 53355
p(t) * p < .05, ** p < .01
Table 6. Mixed Effects Poisson Regression of Gun Seizures (lagged residuals) on Four Violence Measures (Slope Effects only), New York City Census Tracts, 1996-2002a
Total
Homicide Gun
Homicide Total
Assault Gun
Assault Interaction of Time with: Est. t Est. t Est. t Est. t
Gun Seizures, Lagged Residuals .005 4.16 ** .005 3.34 ** .001 0.61 .005 1.59 Second Order Spatial Lag -.017 -1.18 -.018 -0.73 .000 -0.03 .080 4.79 ** Poverty .000 -0.01 .008 0.53 -.007 -0.72 -.003 -0.15 Segregation .004 0.48 .014 1.42 -.016 -2.81 ** -.038 -2.81 ** Social Control .036 2.88 ** .017 1.07 .020 2.05 * .001 0.04 Immigration -.034 -6.15 ** -.047 -6.63 ** .016 3.66 ** -.024 -2.43 * Housing -.020 -2.22 * -.038 -3.35 ** .007 0.96 .034 2.27 *
-2 Log Likelihood 31743.3 37652.4 8883.3 21328
a. Assault measures 1996-2000 only p(t): * p < .05 ** p < .01
Quartiles
1 2 3 4
Total Homicide 1.89 2.53 4.26 8.82Gun Homicide 2.48 2.00 4.47 8.56Total Assault 1.39 2.52 4.21 9.38Gun Assault 1.77 2.39 4.03 9.31
Quartiles
1 2 3 4
Total Homicide 0.38 0.56 0.94 1.50Gun Homicide 0.20 0.33 0.59 0.98Total Assault 3.47 4.74 7.46 12.58Gun Assault 0.39 0.61 1.19 2.37
Mean Gun Seizure Rates per 10,000 Persons by Violence
Quartiles
Mean Violence Rates per 10,000 persons in Surrounding Tracts
by Gun Seizure Quartiles
Table 7. Gun Seizure and Violence Rates by Quartiles, New York City Census Tracts, 1996-2002
Figure 3. Gun Seizure Rates per 10,000 Persons for Four Violence Indices
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Gun Homicide
Total Assault
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Figure 4. Violence Rates by Gun Seizure Quartiles, New York City Census Tracts, 1996-2002
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Gun Homicides
Total Assaults
Gun Assaults
Table 8. Mixed Effects Poisson Regression of Gun Seizures on Four Violence Measures by Gun Seizure Quartile (Slope Estimates Only), New York City Census Tracts, 1996-2002a
1 2 3 4 Model Est. t Est. t Est. t Est. t 1. Total Homicide .005 .52 -.008 -.91 .010 3.06 ** .004 2.78 ** 2. Gun Homicide .005 .30 .001 -.08 .007 1.80 * .004 2.47 ** 3. Total Assault -.001 -.93 .007 1.29 -.0003 -0.11 .0004 .22 4. Gun Assault -.029 -1.12 -.017 -1.25 -.009 -1.11 -.006 1.56 a. Assault measures 1996-2000. All estimates controlled for main effects, spatial lag, and five social structural factors p(t): * p < .05 ** p < .01
Table 9. Repeated Measures ANOVA on Predicted Group Means across Gun Seizure Quartiles, New York City Census Tracts, 1996-2002 Total Homicide
Quartile 1 2 3 4 1 - 2 .110** - 3 .280** .170** - 4 .334** .224** .054 -
Gun Homicide
Quartile 1 2 3 4 1 - 2 .154** - 3 .394** .191** - 4 .449** .295** .104 -
p(F): ** p < .01 * p < .05
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)