For the past eight years, the most prominent of all
federal crime-prevention initiatives has been the Community
Oriented Policing Services (COPS) program. The COPS program was
instituted to give grants to state and local law enforcement
agencies to help them reduce crime by increasing community policing
services. Its stated goal was to put 100,000 additional officers on
America's streets.
Evaluating Effectiveness
Since
the inception of the COPS program, local law enforcement agencies
have used billions of its grant dollars for officer salaries,
computer technology, and clerical support. However, in spite of its
intentions, COPS has not proven successful when its performance has
been measured by standards of social science research. Research by
The Heritage Foundation, the U.S. Department of Justice, and the
U.S. General Accounting Office has found consistently that COPS has
failed to come close to the goal of assigning 100,000 additional
officers for community policing.
The
purpose of this paper is to review recent research regarding the
COPS program.
Research by The Heritage
Foundation
Some
observers claim that the COPS program is a proven success because
crime has declined every year since the program's creation. In May 2001, The
Heritage Foundation's Center for Data Analysis (CDA) published an
evaluation of the COPS program that examined the relationship
between COPS funding and changes in crime from 1995 to 1998.
The
CDA report found that grants used to hire additional officers and
purchase technology were ineffective in reducing violent crime. In
contrast, grants that were narrowly focused and used to target
specific problems--such as domestic violence, youth firearm
violence, and gangs--were somewhat effective in reducing violent
crime. The Heritage
Foundation analysis builds on research that demonstrates that how
the police are deployed is more important in reducing crime than
how many officers are funded.
Research by the University of
Nebraska
Approximately six months after the
publication of the Heritage Foundation's COPS evaluation,
researchers at the University of Nebraska at Omaha and Southwest
Texas State University published a federally funded evaluation of
COPS. This study
(hereinafter referred to as the Nebraska study) was financed
through two COPS office grants totaling over $156,000.
The
Nebraska study found that two types of COPS grants--hiring grants
and narrowly focused grants--reduced crime rates in cities with
populations over 10,000 but that redeployment grants failed to
reduce crime. With regard to smaller cities with populations
between 1,000 and 10,000, the Nebraska study shows that COPS grants
were correlated with higher crime rates. In these cities, hiring
grants were associated with an increase in violent and property
crime while redeployment grants were associated with an increase in
property crime. The results of the COPS-funded research have been
used to support claims about the program's effectiveness.
COMPARING THE HERITAGE AND NEBRASKA
STUDIES
The
Nebraska study was highly critical of prior research that did not
"control for extraneous factors that may be correlated with both
increases in the number of police officers and increases in crime
rates, such as local politics, or fluctuation in the local economy
of cities."
Regrettably, data limitations did not permit the Nebraska study
researchers to improve on the existing research. The Nebraska study
failed to use data that accounted for important socioeconomic and
demographic changes on a yearly basis. It also did not control for
the efforts of local law enforcement.
Ignoring Important Socioeconomic and
Demographic Changes
Data
for all localities for six out of seven socioeconomic variables in
the Nebraska study were not available on a yearly basis. Therefore, rather than
using data for each year between 1994 and 1999, this study held the
following control variables constant at 1990 levels: minority
population percent, single-parent household percent, young people
percent, homeownership percent, and percent of people in the same
house since 1985. In
addition, the 1994 crime rate was used as a control variable.
In a study covering the period 1994 to 1999, the
use of data exclusively from 1990 for most of the control variables
is inappropriate and is likely to reduce the validity of the
findings. By holding controlvariables constant at 1990 levels, the
study starts with outdated information and does not take into
account significant demographic changes that occurred on a yearly
basis between 1994 to 1999. For example, from 1990 to 1999, the
portion of the population accounted for by minorities increased by
almost 16 percent.
Holding most of the control variables
constant at 1990 levels fails to account for the geographic
mobility of Americans. From 1991 to 1998, the percentage of
Americans moving to new residences ranged from 16 percent to 17.3
percent each year.
The Nebraska study's use of 1990 data failed to take into account
many important changes during the past decade that may have
influenced crime rates, such as changes in the minority and youth
populations.
Disregarding the Impact of State and
Local Law Enforcement
Perhaps the most surprising aspect of the
Nebraska study is its assumption that state and local law
enforcement efforts do not influence crime rates. The statistical
model used by the researchers considers only the effect of federal
funds. This approach ignores the impact of state and local
expenditures on policing that dwarf the funds provided through the
COPS program. During the 1994-1999 period, the COPS program had a
nationwide budget of $6.9 billion, but state and local governments
allocated more than $280 billion for police agencies. Put another way, for
every $1 spent on COPS initiatives, over $40 was spent by state and
local governments for police protection.
The
Heritage Foundation used an alternative approach in which the
statistical model took into account state and local investments in
policing. This model used county-level data, which include more
complete information on local spending as well as information on
important socioeconomic factors that is available on a yearly
basis. The Heritage Foundation study found that state and local
police expenditures had a significant impact on the reduction of
crime.
The
Nebraska study's approach tends to bias the results toward a
finding that COPS is more effective than is really the case.
Although the Nebraska study asserted that the Heritage Foundation's
use of county-level data is flawed because "some counties have only
a small number of COPS funded agencies," Heritage analysts focused on localities
that received substantial COPS funding. The median amount of total
COPS funding to the counties in the Heritage Foundation data set
between 1995 and 1998 was $498,664, with 95 percent of the counties
receiving between $424,337 and $553,953. If COPS grants were as effective as the
Nebraska study researchers believe, this amount of COPS funding
within these counties should have had a measurable impact on rates
of violent crime.
Comparison with Other Studies
To
help reconcile the different approaches used by the Heritage
Foundation and Nebraska studies, analysts in the Center for Data
Analysis reviewed 33 studies of the effect of the police on crime
across multiple jurisdictions. (For a list of these studies, see
the Appendix.) All of the studies have been published in academic
journals.
Variable Selection
One
important variable regarding the effect of local law enforcement is
best accounted for by a variable that captures the deterrent effect
of police presence. Deterrence theory holds that increased police
activity deters crime by making criminals believe that the
probability of their arrest and
punishment is higher. This increased risk of detection
decreases the benefits of illegal activities, and criminals who
fear arrest and punishment may have second thoughts before
committing crime.
A
related theory suggests that increased police activity not only
increases deterrence, but also increases the incapacitation of
criminals. Increases
in incapacitation can be achieved by increasing the percentage of
offenses in which offenders are arrested and temporarily removed
from society (crimes that are "cleared by arrest").
Of the
33 studies reviewed, the independent variables estimating the
effect of the police on crime can be placed into three categories:
clearance rates, number of police employees, and police
expenditures. The studies and their respective control variables
for the deterrent effect of the police are presented in Table
1.
Clearance rates are defined as the
percentage of known offenses that result in an arrest of an
offender; they are usually measured on an annual basis. Increased
clearance rates are thought not only to have a deterrent effect, as
some offenders will perceive criminal activity as more risky, but
also to reduce the opportunity for the arrested offenders to commit
additional crimes. After an arrest for a violent crime, offenders
are frequently detained in jail while awaiting trial and, possibly,
incarceration.
Though
clearance rates do not specifically measure the incapacitation
effect, they can be used as a proxy in measuring the effects of
incapacitation on crime. Six studies captured the deterrent effect
of the police by using clearance rates. In 1978, the National Research Council
Panel on Research on Deterrent and Incapacitative Effects
questioned the validity of using risk-of-apprehension ratios such
as clearance rates because of possible measurement error. Measurement error
occurs in clearance rates when police departments underreport known
offenses in relation to arrests. By underreporting offenses, police
departments can artificially inflate their clearance rates and thus
appear to be more efficient in solving crimes.
As a
substitute for clearance rates, police employment levels and
expenditures have been used to estimate the risk of apprehension.
Increasing the number of officers on the beat, measured either
through actual employment levels or through expenditures, is
thought to be a reasonable variable for detecting the deterrence
effect of the police. A total of 19 studies conceptualized the
police variable through the number of police employed, while nine used
police expenditures in estimating the effect of the police on
crime. To control
for the deterrent effect of local law enforcement, the Heritage
Foundation obtained annual state and local law enforcement
expenditures on the county level from the U.S. Census Bureau.
In
response to Heritage Foundation testimony presented before the
Subcommittee on Crime of the U.S. House Committee on the
Judiciary, the
Nebraska study's principal researcher, Dr. Jihong Zhao, attempted
to refute the Heritage criticisms in a letter to Subcommittee
Chairman Lamar Smith (R-TX). Responding to the Heritage criticism
that the Nebraska study failed to control for the efforts of state
and local law enforcement, Dr. Zhao asserts that his study used two
methods to control indirectly for local law enforcement. The first method is
the inclusion of the 1994 crime rate as a control variable.
Dr.
Zhao asserts that "It is reasonable to postulate that the level of
crime rates in individual cities reflect law enforcement efforts in
controlling crime incidents in these cities." This reasoning, however, misunderstands
the relationship between law enforcement agencies and crime. For
example, under this type of reasoning, any city with a crime rate
lower than New York City's would have a better police department
than the New York City Police Department. But while New York City
may have had a higher total crime rate of 4,031 per 100,000
residents in 1999 than Yonkers, New York, with a total crime rate
of 3,169, it would be incorrect to assume that Yonkers had a better
police department.
This sort of reasoning does not account for the dramatic drop in
crime in New York City as a result of innovative policing.
It
should be noted that, with good reason, none of the 33 studies
cited in the Appendix uses crime as a control for the effects of
local law enforcement. Using crime rates to control for the effect
of local law enforcement on crime rates is not a sound technique
because it does not measure the deterrent effect of local law
enforcement. Variables that reflect changes in the risk of
apprehension, such as police expenditures, are in standard use in
the academic literature. The Nebraska study's approach represents a
significant and unjustifiable departure from the current
literature.
The
second method used to control for local law enforcement according
to Dr. Zhao will be discussed in the next section.
Modeling Technique and Data Type
Both
The Heritage Foundation and Nebraska studies examine the effect of
COPS grants on multiple jurisdictions and years. The Heritage
Foundation study used a panel data set. Panel data sets contain
information on multiple units of analysis (for example, counties
and cities) over multiple years. The Heritage panel data set
consists of data on 752 counties, which comprise a majority of the
country's population, over four years (1995 to 1998). Its variables
contain values that are unique to each county and year.
The
Nebraska study contains data on 6,100 cities from 1994 to 1999, but
it is not a true panel data set, because most of the control
variables are held constant at 1990 levels. In his letter, Dr. Zhao
asserts that dummy control variables for each city are used to
measure the effects of local law enforcement on crime rates. In the academic
literature, this type of method is called a "fixed-effects"
analysis.
Fixed-effects analyses can be used to control for
systematic cross-sectional and time-specific differences between
the units of analysis. Specifically, fixed-effects models assist
researchers in controlling for unobserved factors that are not
accounted for by the control variables. The Heritage Foundation and
Nebraska studies employed the fixed-effects technique by using
cross-sectional dummy variables for each unit of analysis to
control for unobserved differences between the units.
Of the
33 studies identified, six used panel data sets. As shown in Section A of Table 2, all
of the academic panel data studies, with one exception, used
control variables that varied on a yearly basis. (The 1989 study by
Joseph Friedman, Simon Hakim, and Uriel Spiegel did not use any
control variables. )
Section B of Table 2 describes the Heritage Foundation and Nebraska
studies. The Nebraska study's use of control variables that do not
vary year by year appears to be unsupported in the academic
literature that examines the effects of the police on crime. After
controlling for appropriate variables, such as local law
enforcement, five out of the six academic studies (Table 2, Section
A) used the fixed-effects model to help control for unobserved
factors.
It is
important to note that each of these fixed-effects studies included
a variable that directly controls for the deterrent effect of the
police. Dr. Zhao's assertion that the use of the fixed-effects
model can be used as a control for the deterrent effect of local
law enforcement is not supported by the academic literature, since
the fixed-effects model is typically used as a technique to enhance
a study, but not as a substitute for appropriate control
variables.
Despite being supported by more than
$156,000 in COPS funds, the Nebraska study adds little to current
knowledge about the COPS program's effectiveness. The study would
be substantially improved if it controlled for the deterrent effect
of local law enforcement and used control variables that were
updated annually.
SUMMARY
The
COPS program, when tested by social science methods, was not shown
to be an effective crime-fighting program; nor has it fulfilled its
measurable goal of putting 100,000 additional officers on America's
streets. The Heritage Foundation's research findings are based on
the best available data for evaluating the effectiveness of the
COPS program. The COPS-funded Nebraska study, however, is
critically flawed; specifically, it failed to account for factors
that may significantly influence crime rates, and its use of
outdated control variables and exclusion of a control for the
efforts of local law enforcement are not supported by the academic
literature.
David B.
Muhlhausen is a senior policy analyst in the Center for
Data Analysis at The Heritage Foundation.