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Documenting and Explaining the 2015 Homicide Rise, National Institute of Justice, 2016

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U.S. Department of Justice
Office of Justice Programs
National Institute of Justice

National Institute of Justice

Documenting and Explaining the 2015 Homicide Rise:
Research Directions
Richard Rosenfeld*

University of Missouri – St. Louis


June 2016

*Dr. Rosenfeld prepared this paper with support from the National Institute of Justice, Office of Justice Programs,
U.S. Department of Justice, under contract number 2010F_10097 (CSR, Incorporated). The opinions, findings, and
conclusions or recommendations expressed in this publication are those of the authors and do not necessarily rep­
resent those of the Department of Justice.
NCJ 249895

U.S. Department of Justice
Office of Justice Programs
810 Seventh St. N.W.
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Loretta E. Lynch
Attorney General
Karol V. Mason
Assistant Attorney General
Nancy Rodriguez, Ph.D.
Director, National Institute of Justice

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TABLE OF CONTENTS
EXECUTIVE SUMMARY ................................................................................................ 2
INTRODUCTION .............................................................................................................. 4
DOCUMENTING THE INCREASE ................................................................................. 5
THE TOP TEN ................................................................................................................. 10
EXPLAINING THE INCREASE ..................................................................................... 11
DRUG MARKETS ........................................................................................................... 12
IMPRISONMENT ............................................................................................................ 16
FERGUSON EFFECT ...................................................................................................... 18
TOWARD A 21ST CENTURY CRIME INFORMATION SYSTEM ............................ 23
APPENDIX: CITY SAMPLE........................................................................................... 25
REFERENCES ................................................................................................................. 26

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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EXECUTIVE SUMMARY
The debate over the size, scope and causes of the homicide increase in 2015 has been
largely free of systematic evidence. This paper documents the scale of the homicide
increase for a sample of 56 large U.S. cities. It then examines three plausible explanations
of the homicide rise: an expansion of urban drug markets fueled by the heroin epidemic,
reductions in incarceration resulting in a growing number of released prisoners in the
nation’s cities, and a “Ferguson effect” resulting from widely publicized incidents of
police use of deadly force against minority citizens. The paper concludes with a call for
the more frequent and timely release of crime information to address crime problems as
they arise.
The homicide increase in the nation’s large cities was real and nearly unprecedented. It
was also heavily concentrated in a few cities with large African-American populations.
Empirical explanations of the homicide increase must await future research based on
year-end crime data for 2015. Several empirical indicators for assessing the explanations
under consideration here are discussed. For example, if the homicide increase resulted
from an expansion in urban drug markets, we should observe larger increases in drugrelated homicides than those committed under other circumstances. If returning prisoners
fueled the homicide increase, that should be reflected in growing numbers of homicides
committed by parolees.
It will be more difficult to empirically evaluate the so-called Ferguson effect on crime
increases, depending on the version of this phenomenon under consideration. The
dominant interpretation of the Ferguson effect is that criticism of the police stemming
from widely publicized and controversial incidents of the use of force against minority
citizens caused the police to disengage from vigorous enforcement activities. Another
version of the Ferguson effect, however, switches the focus from changes in police
behavior to the longstanding grievances and discontent with policing in AfricanAmerican communities. In this interpretation, when activated by controversial incidents
of police use of force, chronic discontent erupts into violence.
The de-policing interpretation of the Ferguson effect can be evaluated with data on
arrests and other forms of self-initiated activity by the police. De-policing should be
reflected in declining arrest rates in cities experiencing homicide increases. Tracing the
pathways from chronic levels of discontent to an escalation in homicide will ultimately
require ethnographic studies in minority communities that reveal, for example, whether
offenders believe they can engage in crime without fear that residents will contact the
police or cooperate in police investigations. Such studies could also disclose other
linkages between discontent, police use of force and criminal violence.
In summary, the following research questions for documenting and explaining the 2015
homicide rise, at a minimum, should be pursued when the requisite data become
available:
•	 How large and widespread was the homicide increase in 2015? Did other crimes
also increase?

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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•	 What conditions drove the homicide increase? Candidate explanations must
account for the timing as well as the magnitude and scope of the increase.
•	 What role, if any, did the expansion of drug markets play in the 2015 homicide
increase? Was there a relative increase in drug arrests and drug-related
homicides?
•	 Did declining imprisonment rates contribute to the 2015 homicide rise? Was the
increase greater in cities with more returning prisoners and among parolees?
•	 What role did the Ferguson effect play in the homicide rise? If de-policing
contributed to the increase, arrest rates should have declined in cities experiencing
the largest homicide increases. An open question is how to evaluate the role, if
any, of community discontent with the police. Ethnographic studies, among other
methods, should be high on the list of research approaches to identify the
mechanisms linking police legitimacy and escalating levels of violence.
Researchers would have been in a better position to begin addressing the 2015 homicide
rise, with evidence rather than speculation, if timely crime data had been available as the
increase was occurring. We would have known whether the homicide rise was confined
to large cities, whether other crimes were also increasing, and whether arrest rates were
falling. The debate over the homicide increase would have been better informed.
Technical impediments to the monthly release of crime data no longer exist. A large and
worrisome increase in homicide should be the catalyst to finally bring the nation’s crime
monitoring system into the 21st century.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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INTRODUCTION
Early in 2015, the local press in several U.S. cities reported that the decades-long crime
decline had been reversed by a sizable increase in homicide. Then, late in the summer,
the New York Times broke the story nationwide (Davey and Smith 2015). Shortly after
the Times account appeared, Attorney General Loretta Lynch called big city mayors and
police chiefs to a meeting in Washington, D.C., to discuss the homicide rise (Byrne
2015). It was there that FBI Director James Comey first publicly speculated that the
increase may have been driven by widely publicized reports of police use of force that
resulted in de-policing. Director Comey repeated the claim a few days later in a speech at
the University of Chicago, where he called attention to a “chill wind” blowing through
the nation’s police departments. He also pointed out, however, that he did not have the
evidence necessary to confirm de-policing or any other explanation of the homicide rise
(Schmit and Apuzzo 2015).
A lively debate in the press soon erupted over the size of the putative homicide increase
and its causes. On one side were commentators who argued that the increase was real and
caused by widespread public criticism of the police, which had made police officers
hesitant to engage in the proactive policing strategies that reduce crime (Mac Donald
2015).1 On the other side were skeptics who argued that the homicide rise had been
overblown and, whatever its magnitude, did not result from a “Ferguson effect” on
vigorous policing (Bialik 2015; Coates 2015; Friedman, Fortier, and Cullen 2015).
Notably absent from the conflicting accounts of the 2015 homicide rise was
comprehensive evidence needed to evaluate the two issues that framed the debate: (1)
Did homicide rates increase and, if so, how large and widespread was the upturn? and (2)
Was the increase caused by hesitancy on the part of police to carry out their crimefighting mission? This paper is organized accordingly.
I begin by documenting the homicide increase in 2015 with data on year-end homicide
rates in 56 U.S. cities.2 I then present three plausible explanations of the homicide rise:
expanding urban drug markets, declining imprisonment rates, and the so-called Ferguson
effect on policing. Only the latter explanation has received significant attention in the
debate over the homicide increase, but prior research has tied crime rate changes to the
violence surrounding urban drug markets and to prison expansion (e.g., Blumstein 1995;
Levitt 1996; Rosenfeld 2011a). In addition, there are at least two ways in which the
Ferguson effect may have unfolded. The dominant interpretation is that the publicity
surrounding recent controversial police killings resulted in de-policing. A second equally
plausible explanation is that, regardless of their effect on police behavior, the police
killings in Ferguson and elsewhere activated longstanding grievances in minority
communities concerning the police and the criminal justice system as a whole, resulting
																																																								
1

Mac Donald later attributed the homicide increase, in part, to statements made by President Obama that

she believed were unduly critical of the police (Mac Donald 2016).

2
I am grateful to Max Ehrenfreund of The Washington Post and Darrel W. Stephens of the Major Cities

Chiefs Police Association for providing the crime data used in this study.


Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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in a “legitimacy crisis” that spurred crime increases. Researchers have also attributed
homicide increases to declining institutional legitimacy (LaFree 1998; Roth 2009).
I present several empirical indicators that can be used to evaluate the alternative
explanations for the 2015 homicide rise. Unfortunately, the evidence needed to carry out
the pertinent research is unavailable as of this writing, and will not be available until
September or October of 2016 when the FBI releases its Uniform Crime Reports (UCR)
for yearend 2015. In the final section of the paper, I argue that it should not be necessary,
well into the 21st century, to wait nine months after the collection year to learn whether
crime rates are increasing and gain some insight into the underlying causes. The press
and advocacy organizations have done due diligence in compiling crime data from local
police departments, but these sporadic and necessarily incomplete efforts are no
substitute for the timely release of comprehensive crime and arrest statistics by the
responsible federal agencies. Had the official crime data been released on a monthly basis
during 2015, the debate over the homicide rise might have produced less heat and more
light.
My focus is on homicide for two reasons. First, with few exceptions (e.g., Friedman,
Fortier, and Cullen 2015), the public debate has largely turned on whether and why
homicide rates may have increased during the past year. Second, homicide is the most
serious and reliably measured crime type for which trend data are available. None of the
arguments in the debate over the homicide rise, however, including the explanations
examined here, is limited to homicide. A Ferguson effect, expanding drug markets or
declining imprisonment rates might have been expected to lead to increases in other
violent crimes or in property crime. The first order of business for future research on the
2015 homicide increase is to extend the range of offenses under consideration beyond
homicide.3

DOCUMENTING THE INCREASE
The data used to determine the size and scope of the homicide increase in 2015 are from
the police departments in 56 large U. S. cities (see fn. 2). The cities are listed in the
Appendix. With the exception of Salt Lake City, Utah (population 190,884), the
population of each city exceeded 250,000 in 2014. The 56-city sample, therefore,
constitutes the bulk of cities in the UCR’s Group I category of cities with populations
greater than 250,000. The sample accounted for fully 92 percent or 4,873 of the 5,305
homicides in the Group I cities in 2014.4
In addition, as shown in Figure 1, the average homicide rates in the 56-city sample and
the UCR Group I cities have trended together for the past two decades. The correlation (r)
between the two trends is an impressive .96. Both series declined through the end of the
																																																								

3

A good start is a study by Pyrooz et al. (2016) that examined changes in each of the FBI’s Part I violent

and property crimes in relation to a possible Ferguson effect.

4
See the 2014 UCR at https://www.fbi.gov/about-us/cjis/ucr/crime-in-the-u.s/2014/crime-in-the-u.s.-2014.


Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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1990s, flattened for a few years, rose slightly through 2007, and fell again through 2009.
Another slight dip followed until 2015, when both series exhibited a notable increase.
The 56-city sample used in this study is clearly a reasonable proxy for the 70-80 cities
that typically constitute the UCR Group I cities with populations over 250,000. At the
same time, the results of this study are limited to those cities and cannot be generalized to
smaller cities, towns and rural areas, where average homicide rates are lower. With that
limitation in mind, we observe that the homicide rate in the sample rose by 16.8 percent
over the previous year. According to preliminary UCR figures, the homicide rate in the
Group I cities increased by 10.5 percent during the first six months of 2015 over the same
period in 2014.5
Depending on the
reliability of the
homicide data obtained
directly from police
departments, a best
guess is that the yearend 2015 homicide rate
for the Group I cities
will be close to the
16.8-percent rise over
2014 observed in the
sample. The question
now is whether an
increase of that
magnitude merits the
attention it has
received from pundits,
advocates and federal
officials.
National attention to
homicide increases in
U.S. cities is not new,
even during the period
of the crime drop since
the early 1990s. A
recent example is the
National Violent Crime
Summit hosted by the
Police Executive
Research Forum
																																																								
5

Computed from data presented in https://www.fbi.gov/about-us/cjis/ucr/crime-in-theu.s/2015/preliminary-semiannual-uniform-crime-report-januaryjune-2015/tables/table-1. The 2015 sixmonth preliminary UCR figures for smaller cities also reveal sizable increases over the previous year. For
example, homicides in cities with populations between 50,000 and 99,000 went up by 8.9 percent.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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(PERF) in Washington during August of 2006 to discuss rising violent crime6 rates across
the nation. PERF issued a report, provocatively titled A Gathering Storm — Violent
Crime in America, that highlighted crime increases in a sample of 55 cities. According to
the report, “For a growing number of cities across the United States, violent crime is
accelerating at an alarming pace” (Police Executive Research Forum 2006; Somers
2006). The Department of Justice initiated an investigation of crime changes in selected
cities, but never publicly issued a report summarizing the results (Rosenfeld 2007).
To gain perspective on the significance of the 2015 homicide increase, it is useful to
compare it with the increases featured in the PERF report. Between 2004 and 2006,
national violent crime rates rose by 3.5 percent and homicide rates increased by 5.4
percent. The comparable increases for Group I cities were .4 percent and 4.8 percent,
respectively. Violent crime and homicide rates then dropped in 2007.7 These homicide
increases are not trivial but they are considerably smaller than those recorded for 2015,
and they were relatively short lived. If increases of this magnitude garnered the attention
of public officials, including the Attorney General (Somers 2006), in 2006, it is not
surprising that the double-digit percentage increase in big-city homicide registered in
2015 would also spark the interest of public officials and the press.
Was the homicide increase in large cities during 2015 “statistically significant”? A study
by Pyrooz et al. (2016) examined crime rates in 81 large cities 12 months before and 12
months after the killing of Michael Brown by a police officer in Ferguson, Missouri, on
August 9, 2014. They concluded that the difference in homicide trends between the two
periods was not statistically significant, although they did find a significant increase in
robbery after the Ferguson incident. By comparison, the difference between the 2015 and
2014 homicide rates for the 56-city sample in the current study is just significant at the
conventional 5 percent threshold in a one-tailed test (p = .05, t = 1.66).
A closer look at the results of the Pyrooz et al. study, however, reveals a somewhat
different conclusion. Table 2 in that study reports a coefficient on the post-Ferguson trend
in homicide of .015 and a standard error of .009, which yields a t-statistic of 1.67, nearly
identical to that in the current study. Given the differences between the two studies in
sample size, sample composition and estimation methods, it is difficult to directly
compare the results. Moreover, tests of statistical significance are technically
unwarranted because neither sample is a random draw from a population. Nonetheless, it
seems reasonable to conclude that the homicide increases revealed in both studies are at
least roughly comparable.
Pyrooz et al. (2016) did acknowledge that homicide had increased in “selected cities”
during the period they investigated and called attention to the elevated variance in city
homicide rates after the Ferguson incident. The results of the current study are similar.
Figure 2 (see page 9) displays the percentage change between 2014 and 2015 in
homicides for the 56-city sample. There is marked variation in these one-year changes.
Forty cities experienced homicide increases and 16 saw declines or, in one case, no
																																																								
6
7

Violent crimes include homicide, rape, robbery and aggravated assault.
See https://www.fbi.gov/about-us/cjis/ucr/ucr.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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change. Homicides in 18 of the cities increased by more than 25 percent; the increase
exceeded 50 percent in 12 cities. The skewed distribution of the homicide changes
indicates that a relatively small number of cities accounted for most of the increase in the
sample. In fact, just 10 cities accounted for two-thirds of the total homicide increase
between 2014 and 2015, as shown in table 1.
Table 1 displays the 10 cities that contributed the largest number of homicides to the total
increase in 2015. Together, the increases in these cities constituted 66.7 percent of the
total increase in the 56-city sample. Had homicides not risen in these cities, it is likely
that the homicide increase of 2015 would have generated far less attention and
controversy. The remainder of this section focuses on these “top ten” contributors to the
homicide rise in large U.S. cities.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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10

THE TOP TEN
The top ten cities not only produced two-thirds of the big-city homicide increase in 2015,
they also experienced a far larger percentage increase than the sample as a whole. The
percentage increases in the top ten ranged from 90.5 percent in Cleveland to 12.9 percent
in Philadelphia. The average homicide increase over 2014 in the top ten was 33.3 percent,
compared with a 16.8-percent rise for the sample as a whole. One-year increases of this
magnitude in the nation’s large cities, although not unknown, are very rare. Cities in the
top ten had experienced one-year percentage increases in homicide that exceeded their
increase in 2015 on only 15 occasions since 1985. The increase in 2015 was greater than
95 percent of the yearly increases these cities had experienced during the previous three
decades.8 If not unprecedented, then, the 33.3-percent homicide rise in the top ten cities
certainly deserves further scrutiny.9
The top ten cities differ from other large cities in other ways as well. As shown in Figure
3 (see page 11), with an average population of roughly one million, the top ten cities are
somewhat larger than the others in the 56-city sample.10 They also have somewhat higher
poverty rates (24.6 percent versus 20.8 percent). The largest difference between the top
ten and other cities in the sample, however, is their race/ethnic composition. The top ten
have larger black populations and smaller Hispanic populations than the other cities. The
relative size of the black population in the top ten is double that in the other cities (40.8
percent versus 19.9 percent). By contrast, Hispanics make up just 15.2 percent of the
population in the top ten compared with 26.4 percent of the population of the remaining
cities in the sample. As we move to a consideration of explanations for the homicide rise
in 2015, these race/ethnic differences merit prominent attention.
In summary, the homicide rise in 2015 in the nation’s large cities was real and, while not
unprecedented, comparatively large. Whether the increase extended beyond the largest
cities remains unknown, although preliminary UCR data for the first six months of 2015
reveal sizable increases in smaller cities as well (see fn. 5). Homicides in the 56-city
sample used in this study increased by 16.8 percent over 2014. Ten cities accounted for
two-thirds of this increase, and together they experienced a 33.3-percent jump in
homicide. These cities have considerably larger black populations and smaller Hispanic
populations than the other cities in the sample. We now turn to three plausible
explanations of the homicide rise: the expansion of urban drug markets, falling
imprisonment rates, and the effects of widely publicized and controversial incidents of
the use of force by the police against minority citizens.
																																																								
8

The 2015 percentage increase in four of the cities (Cleveland, Washington, Milwaukee and Baltimore)

was greater than the increase they experienced during any year since 1985. The 15 yearly homicide

increases that exceeded the percentage increase in 2015 were concentrated in the remaining six of the top

ten cities and constituted just 5.0 percent of the 300 possible yearly increases during the 30-year period (10
cities x 30 years).

9

The 33.3-percent rise in homicides in the top ten cities is statistically significant in a one-tailed test (p =

.04; t = 1.99).



10
The data shown in Figure 3 are from the 2010-2014 combined files of the American Community Survey
(www.census.gov/programs-surveys/acs/)


Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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EXPLAINING THE INCREASE
The study of crime trends is as old as criminology itself. A large body of contemporary
research literature is devoted to explaining the causes and correlates of changing crime
rates (Blumstein and Wallman 2006; Rosenfeld 2011a). The current task, however, is not
to explain a long- or even short-run trend in crime rates, but rather a trend reversal in the
nation’s large cities. Some of the explanatory factors that have been emphasized in the
crime trends literature are poor candidates for explaining the homicide rise of 2015.
Shifts in age composition or the consequences of exposure to lead, for example, unfold
gradually over time and cannot explain why homicide rates would suddenly increase after
falling for over two decades. The same is true of economic conditions, except for the
relatively abrupt changes in income and employment that occur during a recession. The
last recession in the United States, however, ended at least five years before the current
upturn in homicide (see www.nber.org/cycles/main.html). Some evidence suggests that a
drop in consumer confidence contributed to the increase in violent crime in 2005 and
2006 (Rosenfeld and Oliver 2008). Consumer confidence, however, rose from 2014 to

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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2015.11 Crime increases also tend to correspond with rising inflation rates (Rosenfeld and
Levin 2016), but U.S. inflation rates fell from 2011 through the end of 2015.12
It is reasonable to assume that whatever factors lay behind the 2015 homicide rise should
themselves have exhibited comparably abrupt changes at the same time or shortly before.
Among the explanatory factors featured in research on crime trends, the three that are
examined here appear better able than others, at least in principle, to explain the recent
homicide increase. We begin by considering whether the comparatively sudden uptick in
homicide in large cities might have been spurred by a recent expansion in urban drug
markets. The discussion then turns to the possible role of recent changes in imprisonment
rates and, finally, to the Ferguson effect, in both its de-policing and “legitimacy”
versions. Throughout the discussion, several empirical indicators are described that can
be used to evaluate the contribution of these factors to the homicide increase, once the
requisite data become
available.

DRUG MARKETS
The United States is in
the midst of a major
drug epidemic. An
important indicator of
rising drug use and
abuse is the death rate
from drug overdose.
Figure 4 displays the
trend in drug overdose
deaths from 1999 to
2014. The overdose
death rate more than
doubled over the period.
In 2014, more persons
died from drug
overdose than during
any previous year on
record (Rudd et al.
2016). The increase in
drug deaths, in turn,
was driven largely by
the growth in deaths
related to the non																																																								
11

The University of Michigan’s Index of Consumer Sentiment rose from a value of 84.1 in 2014 to 92.9 in
2015 (http://www.sca.isr.umich.edu/tables.html). See Rosenfeld and Fornango (2007) for a study of crime
trends and consumer sentiment.
12
See http://www.usinflationcalculator.com/inflation/historical-inflation-rates/.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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medical use of opioid analgesics (e.g., Oxycontin, Vicodin) and heroin, as shown in
Figure 5. By 2014, opioid and heroin deaths accounted for 61.0 percent of all drug
overdose deaths in the United States (Rudd et al. 2016). Cocaine overdose contributed an
additional 5,415 drug deaths in 2014, but the number of cocaine deaths peaked in 2006.
Beginning in 2012, the number of heroin overdose deaths overtook the number of cocaine
deaths; by 2014, the number of heroin deaths was nearly twice as large (see Figure 5).
As more users enter the market for illicit drugs, the opportunities and incentives for drug
sellers also expand. Disputes among sellers over access to customers, and between sellers
and buyers over price, purity and other terms of trade, often end in violence in illicit
markets where participants have no legal means to resolve disputes (Reuter 2010). In an
influential paper, Blumstein (1995) linked youth homicide increases to the emergence
and spread of the crack cocaine markets in U.S. cities during the 1980s and early 1990s.
As the demand for crack grew, young sellers were recruited into the markets because of
their reduced legal liability. They carried guns to protect themselves from rivals,
customers and street
robbers. As the violence
connected to the crack
markets escalated, other
youth acquired guns to
protect themselves from
an increasingly
dangerous inner-city
environment. A classic
arms race ensued and
youth firearm homicide
rates rose (see also
Blumstein and
Rosenfeld 1998).
Subsequent research has
confirmed the
“Blumstein hypothesis”
linking homicide and the
diffusion of guns to the
expansion of urban drug
markets (e.g., Cork
1999; Messner et al.
2005; Ousey and Lee
2002). The question is
whether similar
dynamics were at play
in the homicide rise of
2015.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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There are reasons, and some evidence, for and against this hypothesis. Urban drug
markets are, or at least were, violent locales. As more buyers and sellers come into
contact in these “stateless” locations, homicide rates should be expected to rise. But some
evidence suggests that changes in illicit drug market transactions, such as the use of cell
phones to connect with customers and effective law enforcement initiatives to shut down
open air street markets, have reduced drug market violence (see Zimring 2011). In
addition, the population groups fueling the growing demand for heroin differ from the
largely inner-city African-American consumers of crack cocaine during the initial years
of the crack era. As shown in Table 2, heroin use rates among non-Hispanic whites more

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

15

than doubled between 2002 and 2013, while heroin use actually fell somewhat among
other race and ethnic groups (see Jones et al. 2015). Prior research has shown that, during
the crack era, the link between expanding drug markets and homicide was strongest in
cities with high levels of economic disadvantage and racial segregation (Ousey and Lee
2002). Evidence that the current heroin epidemic has been confined to the white
population also may be one reason why it has been defined largely as a public health
challenge rather than a criminal justice problem (Cohen 2015).
But the major reason to be skeptical of the view that the expansion of the heroin markets
led to the homicide increase of 2015 is that the heroin epidemic took off several years
before the homicide rise. Heroin overdose deaths were essentially unchanged between
1999 and 2006. They rose gradually over the next few years and then increased sharply
beginning in 2011 (see Figure 5). It is not obvious why the increase in homicide would
lag at least five years behind the explosive growth in the demand for heroin, if the
expansion of urban drug markets spurred the homicide rise.
Whether the homicide rise was produced by drug market expansion or other factors is
ultimately an empirical question for which we do not yet have answers. Strong
conclusions will require ethnographic studies of contemporary drug markets, like those
written about the crack era, that take a close look at the ways in which they may, or may
not, give rise to the violence associated with the crack markets a generation ago
(Bourgois 2003; Contreras 2013). In the meantime, however, several empirical indicators
can be used to gauge whether the recent expansion of drug markets was implicated in the
homicide increase of 2015.
The most obvious indicator for assessing a rise in drug-related crime is the drug arrest
rate. Drug arrests reflect enforcement policy and do not necessarily correspond with
changes in drug law violations. Prior research, however, has revealed a close relationship
between drug arrest rates and other indicators of drug use, such as hospital admissions for
drug overdose (Rosenfeld and Decker 1999). Expanding drug markets should produce
increases in arrests for both drug sales and possession. Arrests for drug abuse violations
actually fell nationwide between 2011 and 2014, when the heroin epidemic was
underway, but the aggregate data combine arrests for all drug types, including
marijuana.13 Researchers can query local police departments for data that partition drug
arrests by drug type. Comparably detailed data for large cities will be available when the
2015 UCR files are archived.
A more sensitive indicator of the possible role of drug market expansion in the 2015
homicide increase is the fraction of homicides that are drug related. Most big city police
departments code homicides by circumstance, including whether the killing was related
to drug use or a drug transaction. The FBI’s Supplementary Homicide Reports also
classify homicides by drug circumstance. Obviously, such classifications require
considerable discretion on the part of crime analysts, but we should expect to see a rise in
the proportion of drug-related homicides if expanding drug markets were a major
contributor to the homicide increase.
																																																								
13

See http://www.bjs.gov/index.cfm?ty=datool&surl=/arrests/index.cfm.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

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IMPRISONMENT
After rising continuously for several decades, the number of state and federal prisoners in
the United States peaked in 2009 and began to decline modestly, as shown in Figure 6
(for source data, see http://www.bjs.gov/index.cfm?ty=nps). In 2014, 1.56 million
persons were serving time in prison, down from the peak of 1.62 million in 2009. Rising
imprisonment rates are associated with declining crime rates, although debate exists
regarding the strength and policy implications of the relationship, as shown by the recent
National Research Council report, The Growth of Incarceration in the United States:
Exploring Causes and Consequences (Travis, Western, and Redburn 2014). Falling
imprisonment rates might then trigger crime increases, assuming the relationship between
imprisonment and crime is symmetrical. Did the growing number of ex-prisoners
returning home contribute to the 2015 homicide increase?
As with the drug market hypothesis, there are reasons for and against assuming that
declining imprisonment was a major contributor to the 2015 homicide rise. Ex-prisoners
have high recidivism rates; the most recent data indicate that two-thirds will be arrested
within three years after
release (Cooper,
Durose, and Snyder
2014). The arrest rates
of released prisoners are
far greater than those of
general population
groups of the same age
and race (Rosenfeld,
Wallman, and Fornango
2005). As more
released prisoners reenter the population,
other things equal,
crime rates should rise.
But all else is rarely
equal, if for no other
reason than some
number of persons will
be entering prison at the
same time others are
released. The crimes
committed by the latter
should be discounted by
the crimes the former
would have committed
had they remained free.
A reasonably accurate
indicator of the net

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

17

contribution of imprisonment to crime, therefore, is the number of persons released from
prison minus the number entering prison during a given period. Figure 7 displays these
figures for the period 2010 to 2014.
With the exception of 2013, prison releases exceeded prison entries during the five-year
period shown in Figure 7. But the net increase in returning prisoners varied considerably,
from fewer than 5,000 in 2010 to more than 28,000 in 2012. The large net increase in exprisoners in 2012 may have contributed to the homicide rise three years later, but the time
lag requires additional explanation. The results of a recent study are generally supportive
of a time lag between imprisonment rates and crime rates. Rosenfeld and Levin (2016)
found that imprisonment rates have nonsignificant effects on crime rates in the short run
but significant effects that unfold over several years. That study, however, focused on
robbery and property crime rates; it is unknown whether similar results exist for
homicide.
Future research on the role of imprisonment in the 2015 homicide rise must address the
variation in prison releases and admissions across states and cities (see
http://www.bjs.gov/index.cfm?ty=nps). Three instructive empirical indicators for
assessing the contribution of imprisonment to the homicide increase are (1) the net
change in the number of prisoners released from and entering prison, (2) the number of
persons on parole and (3)
the fraction of homicides
committed by persons on
parole.
The first two indicators
essentially depict the flow
and stock, respectively, of
ex-prisoners in the
jurisdiction. Published
data on parolees at the
state level are available
from the Bureau of
Justice Statistics’ (BJS’s)
yearly probation and
parole surveys.14 Countylevel data from the
surveys would have to be
obtained under special
arrangement with BJS or
directly from state
corrections departments.
The third indicator
provides evidence of
																																																								
14

See http://www.bjs.gov/index.cfm?ty=tp&tid=1521. The surveys, of course, do not include ex-prisoners
who have “maxed out” their sentences and are not under community supervision.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

18

change over time in the involvement in homicide, both as offenders and victims, of exprisoners under community supervision. If ex-prisoners contributed significantly to the
homicide increase, researchers should observe a corresponding increase in the homicide
rate of persons on parole and in the proportion of homicides committed by parolees in
those cities exhibiting large increases in homicide. These data will have to be compiled
from the records of local law enforcement agencies.

FERGUSON EFFECT
What has become known as the “Ferguson effect” on the homicide increase, as noted, is
subject to considerable controversy and evidence-free rhetoric. The term is also
unfortunate, because it does not only apply to the police killing in Ferguson and because
its precise meaning is unclear. The dominant de-policing interpretation is that highly
publicized incidents of police use of deadly force against minority citizens, including but
not limited to the Ferguson incident, caused police officers to disengage from their duties,
particularly proactive tactics that prevent crime. Interestingly, however, that is not the
interpretation of the individual who evidently coined the term. Sam Dotson, Chief of the
St. Louis Metropolitan Police Department, used the term in an interview with a reporter
in November of 2014, three months after Michael Brown was killed. “It’s the Ferguson
effect,” Dotson said. “I see it not only on the law enforcement side, but the criminal
element is feeling empowered by the environment” (Byers 2014).
It is important to emphasize both arguments Chief Dotson advanced in the interview.15
He stated that the police in St. Louis were redeployed from their normal and more
proactive responsibilities to address protest activities and civil disorder in Ferguson and
elsewhere in the St. Louis area during the months immediately following Brown’s death.
As conditions returned to normal, so did police activity. For example, arrest rates
returned to pre-Ferguson levels after decreasing during the late summer and fall of 2014.
In the view of the St. Louis police chief, changes in police deployment patterns did result
in crime increases in St. Louis in the immediate aftermath of the Ferguson incident. But
he does not believe that his officers engaged in de-policing in the conventional sense of a
work slowdown or reluctance to engage in vigorous, proactive enforcement. That is
where the second point becomes relevant. The Ferguson effect, in his view, was not
simply a matter of altered police behavior. Criminals, according to Chief Dotson, became
“empowered” by the police killing in Ferguson and ensuing protests and civil unrest. The
question then becomes how such feelings and beliefs might have triggered a homicide
increase that persisted at least another year after Ferguson.
Intentionally or not, the St. Louis police chief invoked an important strain of sociological
and criminological thinking in his explanation of the Ferguson effect: the idea that
violence escalates when individuals and communities are alienated from the legitimate
means of social control. When persons do not trust the police to act on their behalf and to
treat them fairly and with respect, they lose confidence in the formal apparatus of social
																																																								
15

The discussion in this section is based on Byers (2014) and personal communication with Chief Dotson.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

19

control and become more likely to take matters into their own hands. Interpersonal
disputes are settled informally and often violently. Honor codes develop that encourage
people to respond with violence to threats and disrespect (Anderson 1999). Predatory
violence increases because offenders believe victims and witnesses will not contact the
police. Individuals engage in “self-help” and entire communities become “stateless”
social locations (Black 1983, 2010).
Randolph Roth (2009) has distinguished the proximate and ultimate causes of historical
changes in U.S. homicide rates. Proximate causes refer to conditions that criminologists
typically point to as risk factors for violence (e.g., economic disadvantage, firearm
carrying, drug and alcohol use). Ultimate causes are the more or less widespread popular
beliefs that government and the legal system are legitimate and worthy of respect, and
that government officials can be trusted. When the perceived legitimacy of government
and trust in officials erode, according to Roth, homicide rates increase. Such historical
periods include the years immediately preceding the American Revolution and the Civil
War. Both Roth (2009) and Gary LaFree (1998) have attributed the rise in homicide
during the 1960s and 1970s to the declining legitimacy of U.S. political institutions.
The police are the front line of government in disadvantaged urban communities.
Following Roth (2009), the ultimate cause of violence in these communities is lack of
confidence in the police. When the police are called to respond to a crime, they arrive at
the scene late or not at all. They do not follow up with vigorous and thorough
investigation, even of the most serious crimes (Leovy 2015). They harass innocent youth.
And, too often, they use force unnecessarily and indiscriminately. What matters is not the
factual accuracy of these beliefs in every instance; what matters is that they can
metastasize into a pronounced “legal cynicism,” especially in disadvantaged AfricanAmerican communities (Sampson and Bartusch 1998). When people believe the
procedures of formal social control are unjust, they are less likely to obey the law (Tyler
2006).
If this complex of “feelings and beliefs,” in Roth’s (2009) terms, is the ultimate cause of
escalations in homicide, the more proximate cause could be widely publicized incidents
of police use of force that seem to confirm the validity of the underlying belief system.
Lack of confidence in the police among African-Americans predates the recent police
killings in Ferguson, Cleveland, New York and elsewhere. But it is likely to be activated
by such incidents, transforming longstanding latent grievances into an acute legitimacy
crisis. If that led to the 2015 homicide increase, we should expect at least four empirical
conditions to hold: (1) the increase should be concentrated in cities with large AfricanAmerican populations, (2) the timing of the increase should correspond closely to
controversial incidents of police use of force against African-Americans, (3) confidence
in the police should be substantially lower among African-Americans than other groups
and (4) the homicide increase should be greater among African-Americans than other
groups.
The available evidence supports the first two expectations. We have seen that 10 cities
with relatively large African-American populations accounted for two-thirds of the

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

20

big-city homicide increase in 2015 (see Table 1 and Figure
3). Further, the homicide increase occurred in the immediate
aftermath of controversial police use-of-force incidents. The
timing of the increase provides stronger support for the
Ferguson effect explanation, in either of its versions, than
for explanations attributing the homicide rise to expanding
drug markets or declining imprisonment. Neither hypothesis
can easily account for the sheer abruptness of the increase in
2015 or, in the case of the drug market explanation, for why
homicide rates did not begin to rise several years earlier. At
the same time, researchers must be open to the possibility
that the homicide increase predated the Ferguson events, at
least in some cities (Rosenfeld 2015).
There is ample evidence in support of the third expectation
regarding African-Americans’ lack of confidence in the
police. As shown in Figure 8, just 37 percent of blacks
compared with 59 percent of whites expressed “a great deal”
or “quite a lot” of confidence in the police in Gallup surveys
conducted between 2011 and 2014.16 The sizable racial gap
in attitudes toward the police is not the result of Ferguson or
other recent events. For example, in 1997, 60 percent of
blacks compared with 30 percent of whites answered “yes”
when asked in Gallup surveys whether the police treat
blacks less fairly than whites, as shown in Figure 9 (see
page 21). The racial difference in responses to this item
increased over the next 10 years. Interestingly, the racial gap
did not change appreciably between 2007 and 2015, the year after the Ferguson incident
and other controversial episodes of police use of deadly force against African-Americans.
Finally, the difference between blacks and whites in attitudes toward the police extends to
the justice system as a whole, as shown in Figure 10 (see page 22). Fully two-thirds of
black respondents and just a quarter of whites told Gallup in 2013 they believe the justice
system is biased against blacks. After Ferguson in 2015, the percentage of blacks who
believe the justice system is biased increased to 74 percent, although the comparable
increase among whites was larger, rising to 42 percent.

																																																								

16

For source data for Figures 8-10, see http://www.gallup.com/poll/175088/gallup-review-black-whiteattitudes-toward-police.aspx.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

21

There is little question that
blacks and whites differ
greatly in their confidence
in the police, belief that the
police treat blacks less
fairly than whites, and
belief that the justice
system is racially biased.
The racial gap in attitudes
toward the police is not a
recent development.
Tensions between the police
and the black community
triggered the urban civil
disorders of the 1960s
(Report of the National
Commission on Civil
Disorders 1968). Lack of
confidence in the police
represents a smoldering
reservoir of discontent
among African-Americans
that is ignited by heavily
publicized episodes of
police use of force — the
ultimate and proximate causes, respectively, of the escalation of violence. This
hypothesis regarding the recent homicide rise merits close scrutiny by researchers, along
with the alternative version of the Ferguson effect that attributes the homicide increase to
de-policing. Finally, if the legitimacy crisis explanation is correct, we should observe
larger increases in homicide among African-Americans than whites or other groups.
Further, the increases should be concentrated in the disadvantaged black communities of
large cities where legal cynicism is most pronounced (Sampson and Bartusch 1998).
It will be easier to empirically evaluate the de-policing hypothesis than the legitimacy
crisis explanation of the 2015 homicide increase. If de-policing was the operative
mechanism, we should observe larger drops in arrests and other self-initiated police
activities in cities that experienced the greatest homicide increases. The arrest data are
readily available from the UCR, or will be when the 2015 UCR data are released in the
fall of 2016. Data on pedestrian and traffic stops, building checks, and other self-initiated
police activity will have to be obtained from local police departments. It should be noted,
however, that the de-policing hypothesis presupposes a very large effect of policing on
crime, large enough to explain homicide increases from de-policing of 50 percent or more
in some cities. Effect sizes of that magnitude far surpass those revealed in research on the
most effective policing strategies to prevent crime (Braga, Papachristos, and Hureau
2014).

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

22

Testing the hypothesis that a police
legitimacy crisis caused the homicide
increase will be more difficult. The four
empirical expectations discussed above
are necessary but not sufficient
conditions to rule out other explanations.
The key question that must be answered
concerns the mechanisms that translate
community discontent with the police
into escalating levels of violence. Very
little is known about this hypothesized
relationship. Does widespread discontent
lead offenders to believe they can commit
crime with impunity? That seems to be
what the St. Louis police chief meant
when he said criminals became
“empowered” by the Ferguson events. Is
community discontent with the police
fertile soil for “stop snitching”
campaigns? Even more basic
criminological questions are at issue.
Was the homicide increase fueled
primarily by offenders and victims with
extensive criminal records or did the
violence spread beyond the already
criminally involved population? In other
words, was the increase spurred by a
growing prevalence of criminal violence or by a heightened incidence of violence among
active offenders?
The latter question might be addressed with data from ongoing longitudinal studies of
delinquency and crime (e.g., Berg et al. 2016; Loeber and Farrington 2011). To determine
whether discontent with the police reduced the willingness of African-Americans to
report crimes to the police, police reporting rates by race can be accessed from the
National Crime Victimization Survey when BJS releases the 2015 data and the results
can be compared with those for previous years and across differing community types.
The best and perhaps only way to address other questions pertaining to the hypothesized
police legitimacy crisis is through ethnographic research in African-American
communities that seeks to disclose how chronic discontent with the police may be
activated by controversial incidents of police use of force and, in turn, may lead to a rise
in violence.
In summary, there are several empirical indicators and methods to evaluate alternative
explanations of the 2015 homicide rise. It may turn out that the three considered here, as
well as others yet to be proposed, are not competing hypotheses so much as interacting
components of a broader explanation. For example, we might expect offenders to feel

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

23

especially “empowered,” not only in the context of community discontent and anger, but
when they also believe, correctly or not, that the police have backed off as a result.
Homicide increases owing to a Ferguson effect might have been greater in cities with
expanding drug markets and a larger pool of recently released prisoners than elsewhere.
The necessary research will take time to carry out and must await the release of key
empirical indicators.

TOWARD A 21ST CENTURY CRIME INFORMATION SYSTEM
At several points in this discussion, reference has been made to the need to wait for the
release of data needed to document and explain the recent homicide increase. The FBI’s
UCR data cannot answer all of the empirical questions raised here, but they can be used
to address some important ones, such as whether arrest rates fell in the large cities
registering homicide increases or, indeed, whether the homicide increase extended
beyond the large cities. FBI Director Comey has pointed to the importance of the data his
agency compiles for understanding and responding to the homicide rise, noting that
“without more reliable data, the task of identifying trends and remedies to fix them is far
more challenging. . . . [I]t’s important, because it gives us the full picture of what’s
happening” (Schmit and Apuzzo 2015).
Imagine how the public debate over the homicide rise might have differed had the FBI
released monthly UCR data one or two months after the collection period. We would
have known whether other crimes in addition to homicide were increasing. We would
know whether smaller cities were experiencing crime increases. We would not have had
to rely on newspaper reporters and policy advocates to gather data from small and
nonrepresentative samples. Assuming the Supplementary Homicide Reports data were
not far behind, researchers would have had some indication of whether drug-related
homicides were on the rise. The debate over de-policing could have been informed by
comparative data on arrest rates. Better and timelier data would not have ended the
debate, but they would have placed it on sounder empirical footing.
There are no longer technical impediments to timely release of the nation’s crime and
arrest data by the FBI. That is largely because the national UCR program no longer
compiles data directly from the 18,000 law enforcement agencies in the country. Rather,
most of the data are compiled, checked and submitted by state UCR programs.17 Many of
the state programs submit the data on a monthly basis and those that do not can be
encouraged to do so. Even if the FBI was able to release timely data for just five percent
of the nation’s law enforcement agencies, roughly 900 jurisdictions, that would constitute
a much larger number of cases than currently available. Researchers could then construct
reasonably representative samples from those data that would be far more useful than the
																																																								
17

According to the UCR Data Quality Guidelines: “For the most part, agencies submit monthly crime
reports, using uniform offense definitions, to a centralized repository within their state. The state UCR
Program then forwards the data to the FBI’s UCR Program” (www.fbi.gov/about-us/cjis/ucr/data-qualityguidelines-new/#_ftn2).

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

24

samples of a few dozen cities that journalists and policy advocates have been able to
stitch together.
The dissemination of timelier crime data that are useful for addressing crime problems as
they arise would require that the FBI return to a practice it abandoned more than 80 years
ago. During the 1930s, the FBI released crime data on a monthly basis (Rosenfeld
2011b). Admittedly, there were fewer law enforcement agencies in the 1930s, but the
data were entered in pen and ink or on manual typewriters and then sent by the local post
office to Washington. If the FBI could release monthly data under those conditions,
surely it can do so in an age of electronic data transfer when local police departments
routinely post recent crime information on their public websites.
Fortunately, the FBI is now working closely with BJS to modernize the nation’s policebased crime data infrastructure.18 A high priority in this cooperative effort should be to
disseminate crime and arrest data on a schedule that makes the data useful for addressing
emerging crime problems. Otherwise, we can be certain that the press and advocacy
organizations will attempt to fill the information void with data of uncertain reliability —
the very problem to which FBI Director Comey has directed attention in his comments on
the recent crime rise. The nearly unprecedented homicide increase of 2015 should be all
that is necessary to finally move the nation’s crime monitoring system into the 21st
century.

																																																								
18

See, e.g., http://www.bjs.gov/content/pub/pdf/NCS-X_FBI_BJS%20Joint_Statement.pdf.

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

APPENDIX: CITY SAMPLE

	

25

Documenting and Explaining the 2015 Homicide Rise: Research Directions	

26

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