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Firearm Ownership and Violent Crime
in the U.S.
An Ecologic Study
Michael C. Monuteaux, ScD, Lois K. Lee, MD, David Hemenway, PhD, Rebekah Mannix, MD,
Eric W. Fleegler, MD
Introduction: Although some view the ownership of firearms as a deterrent to crime, the
relationship between population-level firearm ownership rates and violent criminal perpetration is
unclear. The purpose of this study is to test the association between state-level firearm ownership
and violent crime.
Methods: State-level rates of household firearm ownership and annual rates of criminal acts from
2001, 2002, and 2004 were analyzed in 2014. Firearm ownership rates were taken from a national
survey and crime data were taken from the Federal Bureau of Investigation Uniform Crime Reports.
Rates of criminal behavior were estimated as a function of household gun ownership using negative
binomial regression models, controlling for several demographic factors.
Results: Higher levels of firearm ownership were associated with higher levels of firearm assault
and firearm robbery. There was also a significant association between firearm ownership and firearm
homicide, as well as overall homicide.
Conclusions: The findings do not support the hypothesis that higher population firearm ownership
rates reduce firearm-associated criminal perpetration. On the contrary, evidence shows that states
with higher levels of firearm ownership have an increased risk for violent crimes perpetrated with a
firearm. Public health stakeholders should consider the outcomes associated with private firearm
ownership.
(Am J Prev Med 2015;49(2):207–214) &2015 American Journal of Preventive Medicine
Introduction
Firearm violence is a persistent public health con-
cern in the U.S., with more than 10,000 American
firearm homicides annually,
1
which is the highest
rate among developed, industrialized nations.
2
Firearms
are used in 68% of homicides in the U.S.
1
Firearms are
also frequently used in the commission of other violent
crimes, such as robbery and assault (44.7 and 50.9 events
per 100,000 people, respectively, in 2013).
3
In the wake of recent mass shootings, gun control
debates have intensified. Firearm safety supporters sug-
gest increasing the regulation of firearms to reduce
violent firearm-related crime, whereas others promote
more widespread firearm availability as a deterrent to
crime and to enhance personal defense. However, the
empirical evidence for the relationship between the level
of firearm ownership and the incidence of criminal
activity, albeit extensive, remains controversial. When
considering homicide, one summary of the literature
claimed that “levels of general gun ownership appear to
have no significant net effect on rates of homicide.”
4
By
contrast, other studies have demonstrated an association
between firearm availability and homicide,
5,6
with a
review concluding that “the available evidence is con-
sistent with the hypothesis that increased gun prevalence
increases the homicide rate.”
7
The literature on the association between firearm
ownership rates and non-fatal assault and robbery is
smaller, characterized by methodologic variability and
marked by inconsistent findings. Some evidence shows
that higher levels of gun ownership are associated with
higher rates of robbery with guns, but not with overall
robbery levels.
8,9
In regions with higher levels of gun
From Boston Children’s Hospital (Monuteaux, Lee, Mannix, Fleegler); and
the Harvard School of Public Health (Hemenway), Boston, Massachusetts
Address correspondence to: Michael C. Monuteaux, ScD, Boston
Children’s Hospital, 300 Longwood Avenue (GL 144), Boston MA 02115.
E-mail: michael.monuteaux@childrens.harvard.edu.
0749-3797/$36.00
http://dx.doi.org/10.1016/j.amepre.2015.02.008
&2015 American Journal of Preventive Medicine Published by Elsevier Inc. Am J Prev Med 2015;49(2):207–214 207
ownership, there are higher levels of gun assault, but not
always higher levels of non-gun assault.
10
One study
reported a positive association between household fire-
arm ownership and gun-related assault across 21 coun-
tries,
11
whereas another country-level study found mixed
evidence for a link between firearm ownership and non-
lethal violence.
12
A county-level study found no link
between a firearm ownership proxy measure and gun
crime,
13
but another study found that individuals living
in cities with high levels of gun availability have higher
odds of being the victim of gun assault or gun robbery.
14
Given the ongoing public debate about firearm policy
at the both the federal and state levels, it is important to
commit additional research efforts to examining firearm
ownership in the U.S. and its relationship with violent
criminal outcomes. The association between household
firearm ownership prevalence and non-lethal violent
crimes where a firearm was used is of particular interest.
The objective of this study is to investigate the link
between levels of self-reported U.S. household gun own-
ership and crimes committed with a firearm, including
robbery and non-fatal assault.
Methods
Study Sample
Data were aggregated on household firearm ownership and
criminal perpetration in each of the 50 states for the years 2001–
2002 and 2004 (the only years with available state-level firearm
ownership data). State-level data on firearm ownership were taken
from the Behavioral Risk Factor Surveillance System (BRFSS), a
large, nationally representative, annual survey of the U.S. pop-
ulation, administered by CDC.
15
BRFSS includes 4200,000
respondents annually and provides representative national- and
state-level prevalence estimates for health-related behaviors and
risk factors. In each of the years 2001, 2002, and 2004, BRFSS
included this question: Are any firearms now kept in or around
your home? Include those kept in a garage, outdoor storage area,
car, truck, or other motor vehicle (the 2004 survey did not include
the second sentence). This question was not administered in
California in 2002 or Hawaii in 2004; therefore, these state–year
observations were excluded from the analysis. When generating
state-level estimates, the survey design was taken into consider-
ation by specifying the primary sampling units and the sampling
weights (denoting the inverse of the probability that the observa-
tion is included), to ensure accuracy.
16
Measures
Criminal data were taken from the Uniform Crime Reports
(UCR), a national, annually updated database of reported crimes
across the U.S., administered by the Federal Bureau of Inves-
tigation (FBI).
3
The UCR gathers data on reported crimes
submitted by city, university and college, county, state, tribal,
and federal law enforcement entities.
Although the data are subjected to a rigorous quality control
regimen by the FBI, quality issues have been noted with UCR
data.
17,18
First, not all law enforcement agencies report data,
leading to portions of the population that are not represented. In
2001, 2002, and 2004, the law enforcement agencies participating
in the UCR Program represented 92%, 93% and 94%, respectively,
of the U.S. population , with a median state-level coverage of 98.5%
(interquartile range=92.5%, 99.8%). Also, the data only represent
criminal events that are reported to law enforcement agencies. The
nationally representative National Crime Victimization Survey
indicates that, for many crimes, a proportion of victims do not
report the incident to authorities.
19
To mitigate these issues, this investigation was limited to crime
outcomes that: (1) are most likely documented by law enforce-
ment
20
; (2) are compiled from law enforcement agencies that
submitted complete data throughout the year under study; and (3)
have a hypothesized relationship to firearm ownership. These were
robberies committed with a firearm and assault committed with a
firearm. Thus, these analyses assumed that for each observation
(i.e., each state–year), the populations within jurisdictions that did
not provide data to the UCR did not differ from those that did in
terms of the prevalence of firearm ownership. The potential impact
of this assumption increased as the proportion of state-level
populations represented by UCR data decreased.
UCR estimates of the annual, state-level populations (derived
from the U.S. Census) represented by the agencies that contributed
data to compile the count of the given outcome were used. Census
data were used to capture annual, state-level estimates of demo-
graphic factors previously associated with firearms,
21
including age
(percentage aged o25 years), race (percentage of blacks), ethnicity
(percentage of Hispanics), sex, median household income, pop-
ulation density (population per square mile of land area),
education (percentage completing at least high school), poverty
(percentage below the federal poverty level), and urbanicity
(percentage living in an urban area).
22
Statistical Analysis
The number of each specific crime type reported for each state in
each year of the study was obtained. A negative binomial
regression model was estimated, with the state-level count of
criminal offenses as the dependent variable and the log of the
population values as the offset (coefficient constrained to 1). A
negative binomial model was chosen to account for the over-
dispersion in the outcome variable, a condition that can lead to
underestimated standard errors in Poisson models. To verify the
model selection, a likelihood ratio test of the overdispersion
parameter, α, was performed. Evidence to reject the null hypoth-
esis that α¼0 indicates that the negative binomial model is
preferred over Poisson. For each of the four models (outcomes
of assault, robbery, homicide, and homicide with a firearm), the
likelihood ratio test supported the use of negative binomial models
over Poisson models (all p-values o0.001).
Gun ownership (divided into quintiles and estimated as dummy
variables with the lowest quintile set as the referent) was modeled
as the independent variable. Dummy variables, as opposed to a
continuous variable, were chosen to capture relationships between
firearm ownership and crime rates that may not be linear.
Demographic factors (age, race, ethnicity, sex, median household
income, population density, education, poverty, and urbanicity)
Monuteaux et al / Am J Prev Med 2015;49(2):207–214208
www.ajpmonline.org
that have previously been shown to be associated with violent
crime and firearm ownership were included as covariates. Models
were also adjusted for year and geographic region (Northeast,
Midwest, South, and West). Finally, to account for spatial
associations among states, adjustment was made for the firearm
ownership levels of neighboring states. That is, for each state, the
mean ownership rate of all geographically adjacent states was
calculated, and this variable was included as a covariate in the
model. For states without adjacent geographic neighbors (Alaska
and Hawaii), the value of the closest state (Washington for Alaska
and California for Hawaii) was used. Each state provided year-
specific values for all terms in the model.
As a secondary analysis, two additional outcomes were also
examined: overall homicide and homicide committed with a
firearm. These were secondary outcomes because the data were
compiled from a subset of jurisdictions within each state from
which supplementary homicide data were available. Specific
population estimates for these were not provided. Overall state-
level population estimates from the Census were used for these
outcomes.
Given that these data included multiple observations for each
state (i.e., one observation per state per year), the assumption of
independent observations may not hold. To accommodate these
data, clustered sandwich SE estimates were used, which allow for
intrastate correlation. All data analyses were performed using
STATA SE, version 12.1.
Results
The rates of reported violent crimes in the U.S. during the
study period (2001, 2002, and 2004) were 505, 495, and
464 per 100,000 individuals, respectively. Overall violent
crime rates ranged from 78.2/100,000 (North Dakota,
2002) to 822.6/100,000 (South Carolina, 2002), with a
median of 371.7/100,000. Homicide rates ranged from
0.8/100,000 (North Dakota, 2002) to 13.3/100,000 (Loui-
siana, 2002), with a median of 4.6/100,000.
There was wide variability across states in the per-
centage of households with a firearm (Table 1), ranging
from 65.5% in Wyoming in 2004 to 8.7% in Hawaii in
2001. Across time, there was little change in gun own-
ership rates within states, and only a 0.6% change
nationally from 2001 to 2004. The 148 observations that
had firearm ownership data available (i.e., each state, by
year, except California in 2002 and Hawaii in 2004) were
categorized into quintiles according to firearm ownership
rates: 8.7%–25.5% (n¼28), 26.2%–37.1% (n¼30), 37.5%–
42.8% (n¼31), 42.9%–48.6% (n¼29), and 50.7%–65.5%
(n¼30).
Association Between State-Level Firearm
Ownership and Violent Crime Rates
Results from the multivariate regression models predict-
ing state-level crime rates are summarized in Table 2.
Table 1. Self-Reported Household Firearm Ownership
Prevalence Across States in the U.S., by Year
State
Percentage of
households with a
firearm Change
(delta),
2001–20042001 2002 2004
Alabama 51.7 57.9 52.2 0.5
Alaska 57.8 60.9 59.8 2.1
Arizona 31.1 37.0 32.3 1.3
Arkansas 55.3 58.7 58.8 3.5
California 21.3 —20.1 –1.2
Colorado 34.7 34.8 34.6 –0.1
Connecticut 16.8 16.4 18.1 1.3
Delaware 25.5 27.1 26.3 0.8
Florida 24.5 26.6 25.2 0.8
Georgia 40.3 41.5 40.3 0.0
Hawaii 8.7 10.2 —1.5
Idaho 55.3 57.1 55.7 0.4
Illinois 20.2 21.2 20.7 0.5
Indiana 39.1 39.6 38.5 –0.6
Iowa 42.8 44.4 45.7 2.9
Kansas 42.1 44.2 42.8 0.7
Kentucky 47.7 48.6 47.7 0.0
Louisiana 44.1 46.3 45.0 0.9
Maine 40.5 41.5 40.3 –0.2
Maryland 21.3 22.5 21.7 0.4
Massachusetts 12.6 12.9 11.5 –1.1
Michigan 38.4 40.7 40.8 2.4
Minnesota 41.7 45.0 41.2 –0.5
Mississippi 55.3 55.0 54.6 –0.7
Missouri 41.7 45.8 44.2 2.5
Montana 57.7 62.1 62.6 4.9
Nebraska 38.6 42.3 45.4 6.8
Nevada 33.8 32.6 34.0 0.2
New
Hampshire
30.0 31.1 31.0 1.0
New Jersey 12.3 11.5 11.4 –0.9
New Mexico 34.8 40.1 39.7 4.9
New York 18.1 18.4 18.5 0.5
(continued on next page)
Monuteaux et al / Am J Prev Med 2015;49(2):207–214 209
August 2015
Higher rates of firearm ownership were positively asso-
ciated with rates of firearm-related assault, with each
quintile exhibiting a significantly increased risk relative
to the lowest, referent quintile. Relative to the states in
the lowest quintile of ownership (i.e., the lowest firearm
ownership category), states in the highest quintile had a
rate of firearm-related assaults that was 6.8 times higher.
Likewise, higher rates of firearm ownership were asso-
ciated with significantly increased rates of firearm-related
robbery across the second, third, and fourth quintiles.
Three-year averages of state-level firearm ownership and
firearm-related robbery and assault rates are depicted in
Figure 1.
Higher levels of firearm ownership were also associated
with a significantly increased risk for overall homicide.
Furthermore, firearm ownership was significantly associ-
ated with increased firearm-related homicide, with each
quintile associated with successively higher risk (Table 2).
These analyses were repeated with the proportions of
state-level populations represented by UCR data
included as an additional covariate. The results for
firearm-related assault and robbery did not change,
continuing to show a significant positive association with
firearm ownership, except that for robbery, the estimate
for the fifth quintile became significant as well (incidence
rate ratio [IRR]¼3.92, 95% CI¼1.34, 11.44). For the
overall homicide outcome, the comparison of the fifth
quintile to the referent quintile failed to achieve statistical
significance (IRR¼1.93, 95% CI¼0.94, 3.98). The
remaining results were unchanged, indicating increased
risk for overall and firearm-related homicide with higher
levels of state-level firearm ownership.
Longitudinal Prediction of State-Level Violent Crime
Rates Using Firearm Ownership
Although the association between firearm ownership and
an increased risk for firearm-related assault and robbery
is consistent with the hypothesis that firearm availability
contributes to firearm-related crime, it is also plausible
that increased rates of crime motivate the acquisition of
firearms in the interest of protection. As one approach to
address this ambiguity, another model was estimated
using firearm ownership in 2001 to predict violent crime
rates in 2002 and 2004, adjusting for the same demo-
graphic factors. As shown in Table 3,firearm ownership
in 2001 was significantly associated with increased rates
of firearm-related assault, robbery, and homicide, as well
as overall homicide.
Discussion
This study tested the hypothesis that private firearm
ownership at the state level serves as a deterrent to
criminal activity, with firearm ownership measured by a
nationally representative self-report survey and crime
measured by official law enforcement agency reports.
These results do not support the hypothesis that higher
rates of firearm ownership are associated with lower
firearm-related assault, robbery, or homicide rates. To
the contrary, evidence was found for a positive associa-
tion, in which states with greater levels of private firearm
ownership experienced greater rates of firearm-related
violent crimes.
These results are consistent with studies finding a
positive association between city-level gun availability,
the individual risk for gun-related assault and rob-
bery,
14,23
and an increased risk for firearm assault
victimization and possessing a firearm at the time of
the crime.
24
The present findings are partially consistent
with a study of gun availability in South Carolina in
1991–1994,
13
which found an association between illegal
Table 1. Self-Reported Household Firearm Ownership
Prevalence Across States in the U.S., by Year (continued)
State
Percentage of
households with a
firearm Change
(delta),
2001–20042001 2002 2004
North Carolina 41.3 41.6 39.4 –1.9
North Dakota 50.7 54.5 56.2 5.5
Ohio 32.4 32.2 34.0 1.6
Oklahoma 42.9 45.0 46.5 3.6
Oregon 39.8 40.3 39.8 0.0
Pennsylvania 34.7 36.7 35.1 0.4
Rhode Island 12.8 13.5 12.4 –0.4
South Carolina 42.3 45.6 43.3 1.0
South Dakota 56.6 60.4 59.9 3.3
Tennessee 43.9 47.0 46.6 2.7
Texas 35.9 36.4 37.1 1.2
Utah 43.9 45.5 44.8 0.9
Vermont 42.0 45.7 43.8 1.8
Virginia 35.1 36.5 37.5 2.3
Washington 33.1 36.7 34.0 0.9
West Virginia 55.4 58.2 58.5 3.0
Wisconsin 44.4 44.5 43.0 –1.5
Wyoming 59.7 63.1 65.5 5.8
Overall 32.2 34.9 32.8 0.6
Note: Values in table represent estimated prevalence.
Monuteaux et al / Am J Prev Med 2015;49(2):207–214210
www.ajpmonline.org
gun availability and gun crime, but not with lawful gun
availability. This discrepancy may be the result of
methodologic differences in the measures of gun preva-
lence (a survey measure of ownership versus a count of
concealed weapon permits). These findings are also
partially consistent with a study of 21 developed coun-
tries (including the U.S.) that found an association
between firearm ownership and rates of gun-related
assault, but not robbery.
11
These findings are similar to studies examining the
link between firearm ownership and firearm-related
homicide, despite methodologic differences. Miller and
colleagues
5,6
reported a positive relationship between
firearm ownership and overall homicide as well as
firearm homicide across states and regions. Another
study found that stronger state-level firearm control
legislation was associated with decreased firearm-
related suicides and homicides.
25
Whereas homicides
were measured using death certificate data in Miller
et al.
5,6
and Fleegler and colleagues,
25
law enforcement
crime reports were used in the present study. This study
is also consistent with that of Siegel et al.,
26
which found a
positive association between state-level non-stranger
homicide and firearm ownership. Another study found
Table 2. Association Between State-Level, Self-Reported Firearm Ownership and Violent Crime Reported to Law Enforcement,
2001–2002, 2004
State-level covariates
a
Violent crime outcome
Assault with a firearm
a
Robbery with a firearm
a
Homicide
b
Homicide with a firearm
b
Firearm ownership
1
st
Quintile (least) ref ref ref ref
2
nd
2.88 (1.31, 6.22) 2.89 (1.46, 5.75) 1.56 (1.09, 2.23) 1.87 (1.21, 2.91)
3
rd
4.23 (1.44, 12.41) 3.33 (1.39, 8.00) 1.81 (1.18, 2.78) 2.22 (1.29, 3.81)
4
th
5.91 (1.78, 19.57) 3.75 (1.55, 9.09) 2.18 (1.44, 3.29) 2.74 (1.62, 4.63)
5
th
(greatest) 6.77 (1.53, 29.92) 2.72 (0.87, 8.57) 2.08 (1.18, 3.66) 2.84 (1.34, 6.04)
Year 0.97 (0.91, 1.03) 0.92 (0.87, 0.98) 0.99 (0.95, 1.03) 0.99 (0.95, 1.04)
Household income 0.99 (0.94, 1.04) 1.01 (0.96, 1.07) 1.01 (0.98, 1.04) 1.01 (0.98, 1.04)
Percent male 1.02 (0.62, 1.68) 1.12 (0.74, 1.71) 1.14 (0.85, 1.52) 1.06 (0.74, 1.53)
Percent black 1.04 (1.01, 1.06) 1.05 (1.03, 1.08) 1.05 (1.03, 1.06) 1.05 (1.04, 1.07)
Percent Latino 1.02 (1.00, 1.05) 1.01 (0.99, 1.04) 1.01 (1.00, 1.03) 1.01 (1.00, 1.03)
Percent o25 years 0.94 (0.85, 1.04) 0.95 (0.89, 1.01) 0.94 (0.90, 0.98) 0.93 (0.89, 0.98)
Percent ZHS education 0.99 (0.91, 1.06) 0.90 (0.84, 0.97) 0.95 (0.89, 1.01) 0.93 (0.87, 0.99)
Percent urban 1.03 (1.00, 1.06) 1.03 (1.01, 1.06) 1.02 (1.00, 1.04) 1.03 (1.00, 1.05)
Percent poverty 1.01 (0.90, 1.12) 0.97 (0.85, 1.11) 1.01 (0.94, 1.08) 0.98 (0.91, 1.06)
Population density 1.00 (1.00, 1.00) 1.00 (1.00, 1.00) 1.00 (1.00, 1.00) 1.00 (1.00, 1.00)
Region
Northeast ref ref ref ref
Midwest 1.87 (0.95, 3.68) 1.91 (0.98, 3.70) 1.25 (0.77, 2.02) 1.32 (0.75, 2.32)
South 2.34 (1.15, 4.78) 1.36 (0.59, 3.14) 1.00 (0.53, 1.88) 1.01 (0.50, 2.05)
West 2.30 (1.00, 5.28) 1.44 (0.56, 3.66) 1.36 (0.77, 2.39) 1.42 (0.74, 2.72)
Border ownership
c
0.98 (0.96, 1.01) 0.99 (0.95, 1.02) 0.99 (0.97, 1.01) 0.99 (0.97, 1.01)
Note: Values in table represent incidence rate ratio (95% CI); boldface indicates statistical significance (po0.05).
a
Illinois did not contribute crime data to this analysis; rates are based on Uniform Crime Reports population estimates of reporting jurisdictions.
b
Florida did not contribute crime data to this analysis; rates are based U.S. Census annual state-level population estimates.
c
Mean firearm ownership rate of all geographically adjacent states.
HS, high school
Monuteaux et al / Am J Prev Med 2015;49(2):207–214 211
August 2015
an association between the repeal of Missouri’s handgun
purchaser licensing law (thereby increasing firearm
availability) and an increase in firearm homicides, using
both death certificate data and UCR data to measure
homicide.
27
Also, a study using a proxy of state-level
firearm ownership (i.e., a composite of a firearm suicide
measure and the hunting license rate) found an associ-
ation with total homicides and firearm-related
homicides.
28
There was a slight increase in overall firearm owner-
ship in 2002 (35%) relative to 2001 (32%), with 45 states
reporting an increase in ownership. These data do not
seem to be indicative of a national upward trend in
ownership, given that the overall prevalence dropped
back to 32.8% in 2004. It is difficult to infer what might
have instigated the increase in 2002, especially given that
the observed delta is compatible with the margin of error
inherent in the survey design from which the data are
derived.
Limitations
These results should be considered in the context of
methodologic limitations. First, the results are susceptible
to the biases and limitations inherent to ecologic stud-
ies.
29
However, consistent with the ecologic findings,
evidence from an individual-level study found an asso-
ciation between carrying a firearm and being injured in a
firearm-related assault.
24
Second is the use of state-level
data as opposed to more granular data (e.g., county- or
city-level data) that better account for differences
between urban and rural areas in violent crime and
Figure 1. Adjusted mean firearm-related assault and robbery rates per 100,000 persons (over years 2001, 2002, and 2004).
No data available for firearm-related assault or robbery rates in Illinois. Colors represent quintiles of specificfirearm-related crimes. Labels
demonstrate quintiles of mean firearm ownership rates with mean percent ownership in parentheses.
Table 3. State-Level, Self-Reported Firearm Ownership in 2001 Predicting Violent Crime Reported to Law Enforcement in
2002 and 2004
Quintiles of firearm
ownership
Assault with a
firearm
a
Robbery with a
firearm
a
Homicide
b
Homicide with a
firearm
b
1
st
(least) ref ref ref ref
2
nd
3.26 (1.42, 7.48) 3.72 (2.04, 6.80) 1.97 (1.44, 2.71) 2.19 (1.46, 3.28)
3
rd
5.06 (1.17, 21.9) 3.84 (1.54, 9.58) 2.03 (1.19, 3.47) 2.36 (1.26, 4.42)
4
th
5.68 (1.18, 27.4) 6.86 (2.72, 17.3) 2.69 (1.33, 5.46) 3.35 (1.52, 7.36)
5
th
(greatest) 7.25 (1.16, 45.2) 5.23 (1.62, 16.9) 2.37 (1.08, 5.20) 3.09 (1.15, 8.26)
Note: Values in table represent incidence rate ratio (95% CI); boldface indicates statistical significance (po0.05). All models adjusted for year, median
household income, sex, race, ethnicity, age, education, urbanicity, poverty, population density, region, and bordering state ownership.
a
Illinois did not contribute crime data to this analysis; rates are based on Uniform Crime Reports population estimates of reporting jurisdictions.
b
Florida did not contribute crime data to this analysis; rates are based U.S. Census annual state-level population estimates.
Monuteaux et al / Am J Prev Med 2015;49(2):207–214212
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firearm ownership. To account for this, models were
adjusted for state-level urban population residence. Also,
these data, though more recent than other published
studies, are still almost a decade old as of this writing.
This study was limited to the use of 10-year-old data
because BRFSS stopped including firearm questions in
2004. However, it is unlikely that temporal changes
would alter the pattern of results if repeated with
contemporaneous data. Also, the use of UCR data only
allows evaluation of the occurrence of reported crimes.
The present study examined serious violent crimes
(aggravated assault, robbery, and homicide) that are
most likely to be reported to law enforcement authorities.
Though the attenuation, if any, of crime rates as a result
of non-reporting could have caused a reduction in
precision, it was unlikely to be differential with respect
to firearm ownership, and should not invalidate the
results. Although a wide range of demographic and social
factors were controlled to account for interstate differ-
ences, it is possible that, as in all observational research,
residual confounding remained in the model estimates,
such that the associations reported herein may have been
spurious. However, it is unlikely that residual confound-
ing could account for the magnitude of some effects
reported. To adjust for geographic effects, an attempt was
made to control for U.S. census region. Although this is a
gross geographic measurement, more specific measures
could not be used, given that data were analyzed at the
state level. Finally, these data do not allow investigation
of the temporal association between firearm ownership
and crime rates. Elevated crime rates could have moti-
vated the private acquisition of firearms in the interest of
self-defense and protection. The longitudinal analysis
showing that firearm ownership in 2001 predicts crime in
later years provides some assurance about the direction
of the effect, but is not adequate to completely rule out
the possibility of reverse causation. Given the methodo-
logic limitations of this study, especially those inherent in
its ecologic design, this study should be replicated with
more recent, individual-level data, as recently proposed
by President Obama’s Executive Action on gun
violence.
30
Conclusions
These analyses do not support the hypothesis that
firearm ownership deters violent firearm crime. Instead,
this study shows that higher levels of firearm ownership
are associated with higher rates of firearm-related violent
crime. Public health and legislative stakeholders should
consider these results when responding to or engaging in
the gun control debate. Further individual-level, epide-
miologic research is needed to confirm these results.
Dr. Hemenway received funding from the Joyce Foundation to
conduct and disseminate research on firearms. The study
sponsor had no role in study design; collection, analysis, and
interpretation of data; writing the report; and the decision to
submit the report for publication.
No financial disclosures were reported by the authors of
this paper.
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