U.S. Department of Justice
Office of Justice Programs
Bureau of Justice Statistics
Technical Report
Crime and Victimization in the Three Largest Metropolitan
Areas, 1980-98
February 2005, NCJ 208075
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This file is text only without graphics and many of the tables.
A Zip archive of the tables in this report in spreadsheet format
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.pdf format are available from:
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By
Janet L. Lauritsen, Ph.D.
Fellow, BJS and Professor, University of
Missouri-St. Louis
Robin J. Schaum
University of Missouri-St. Louis
Introduction
For more than three decades, the Nation has had two national indicators
of crime: the Uniform Crime Reporting (UCR) program and the National
Crime Victimization Survey (NCVS). The UCR program contains information that
is voluntarily provided by police departments and forwarded to the FBI. The
NCVS gathers information from a nationally representative sample of persons
age 12 or older to produce estimates of crime that are independent of the
recording practices of criminal justice systems. Data from the two programs
are routinely used together to provide a more complete assessment of crime
in the United States.***Footnote 1: In this report the terms "police data"
and "UCR data" are used interchangeably. For more detail about the UCR and
NCVS programs, see "The Nation's Two Crime Measures," Bureau of Justice
Statistics, 2003, NCJ 122705.***
Annual estimates of the number of crimes derived from NCVS data have often
been higher than the annual counts in the UCR. There are several reasons why
this may occur. Most importantly, the NCVS data include crimes that are not
reported to the police.***Footnote 2: For more details, see Hart and Rennison
(2003), Reporting Crime to the Police, 1992-2000, Bureau of Justice
Statistics, NCJ 195710.*** According to recent estimates, approximately 51%
of violent victimizations and 64% of property victimizations are not reported
to the police. In addition, NCVS counts may be higher if police departments
do not record all of the incidents that come to their attention or do not
forward the reports to the national UCR program. Indeed, increased knowledge
about crimes not reported to the police and assessments of the reliability
of police data were two important reasons for the development of the crime
survey in the early 1970's.
For some types of crimes in the NCVS and the UCR, it is possible to
reconcile apparent discrepancies in annual estimates by taking into
account differences in the coverage of both data series and adjusting the
NCVS counts to include only those incidents said to have been reported
to the police. When such adjustments are made, levels and trends in
burglary, robbery, and motor vehicle theft appear similar in the NCVS and
UCR. On the other hand, UCR and NCVS levels and trends in aggravated assault
and rape continue to exhibit discrepancies after these kinds of adjustments
are made. Remaining differences in levels or trends in aggravated assault
and rape may reflect broader changes concerning the public's willingness to
report crime to the police, the ways in which police departments record
crime, the quality of victimization survey data, or other factors. It is
clear that the differences in the methodologies of the UCR and NCVS programs
must be considered when assessing both levels and trends of crime in the
Nation.
When State and local governments are interested in assessing levels or
trends in crime in their own areas, they typically rely solely on police
data because victimization survey data are rarely available for places other
than the Nation as a whole. The collection of reliable crime survey data
is costly and most State and local governments have not had the resources
to conduct their own victimization surveys, especially on an annual basis.
Knowing that crime may not be reported to the police or fully recorded, many
wonder whether police-based estimates for local areas provide an accurate
foundation on which to assess levels or short-or long-term trends in crime.
In addition, many wonder whether conclusions drawn from national police and
victim survey data also apply to their local areas.
To examine how police records compare to victimization survey estimates for
places other than the Nation as a whole, the Bureau of Justice Statistics
(BJS) and the U.S. Census Bureau have developed special subsets of NCVS data
that are capable of providing survey-based estimates of crime for the
largest metropolitan areas in the country. This report compares NCVS and
police estimates of burglary, robbery, and aggravated assault for the
country's three largest metropolitan areas – New York, Chicago, and Los
Angeles -- for 1980 through 1998. The features of the NCVS sample limit the
UCR-NCVS comparisons to the core counties that comprise each of these
metropolitan areas (described below). These comparisons can be used to inform
the public about the levels and trends in criminal victimization in these
three areas. They also provide information about the correspondence between
police and victim survey data throughout the 1980's and 1990's for the New
York, Chicago, and Los Angeles areas.
Characteristics of the data
NCVS estimates
The NCVS, and its predecessor, the National Crime Survey (NCS), are
household-based surveys designed to gather information about victimization
directly from the public. A random sample of U.S. households is generated
using a multistage stratified sampling procedure. The result is a
representative sample of households and persons ages 12 or older living in
households.***Footnote 3: Persons not living in households, such as
homeless, institutionalized or incarcerated persons, are not included in the
sample design.*** The Census Bureau develops the sample and administers the
survey for BJS. The sampling strategy for the NCVS is developed explicitly
to provide national estimates of criminal victimization. Generally speaking,
the sample design is capable of providing local area estimates of crime only
for certain places. Heavily populated metropolitan areas constitute unique
self-representing portions of the sample; as a result, it is possible to use
the data from the largest of those areas to form reliable survey-based
estimates of crime for those places.***Footnote 4: The NCVS sample is
generated in two stages. During the first stage, primary sampling units
(PSU's) are designated to reflect metropolitan areas, counties, and
groups of counties. Larger PSU's (reflecting metropolitan areas) are
termed self-representing (SR) and are automatically included in the
sample. Smaller PSU's (non-self-representing or NSR PSU's) are
grouped together in similar strata based on known Census geographic
and demographic characteristics. From the NSR PSU's, sample PSU's
are selected by probability proportionate to population size.***
Two important limitations of the NCVS metropolitan area data should be
noted. First, the boundaries of metropolitan areas often change due to
population shifts and development patterns. To ensure that metropolitan
area victimization rates remain comparable over time, it is necessary to
restrict the geographic boundaries of the areas to the core counties that
remained continuously part of each metropolitan area from 1980 through
1998. For the New York core county area, the sample includes residents
from Bronx, Kings, New York, Queens, Richmond, Putnam, Rockland, and
Westchester Counties.***Footnote 5: For an extensive analysis comparing UCR
and NCVS rates for New York City, see Langan and Durose, "The Remarkable
Drop in Crime in New York City," ISTAT (Italy's National Institute of
Statistics) meeting "per una societa pie secura," Rome, December 3-5,
2004.*** For the Chicago core county area, residents are selected from the
city and Cook, DuPage, and McHenry Counties. For the Los Angeles core county
area, residents of the city and Los Angeles County form the sample used in
these victimization estimates.
Second, compared to the national sample, the number of persons interviewed
within each metropolitan area in a year is relatively small. Altogether
these three metropolitan core county areas constitute roughly 9.5% of the
U.S. population. Sample size places statistical limitations on the types of
crimes that can be reliably estimated for each metropolitan area and year.
The three crimes that occur with sufficient statistical regularity to permit
comparisons with police data are burglary, robbery, and aggravated assault.
To maximize the reliability of the NCVS metropolitan area estimates of
burglary, robbery, and aggravated assault victimization, 3-year moving
averages are used for NCVS crime rate estimates.
Police estimates
Police counts of burglary, robbery, and aggravated assault in each
metropolitan area are based on offenses known to the police departments with
jurisdiction in each of the core county areas.***Footnote 6: Because police
departments voluntarily submit data to the UCR a large amount of data is
missing across time and places. This missing data issue made it difficult to
collect consistent data across all of the counties over the 20-year period.
For this reason, the police data used here for the metropolitan core county
areas of New York and Chicago were gathered from their respective State
criminal justice websites rather than from the UCR reports. The New
York metropolitan area police data were retrieved from the New York
State Division of Criminal Justice Services at
. The Chicago metropolitan area
police data were retrieved from the Illinois Criminal Justice Information
Authority at . The Chicago core
county police data were not complete for 1979 through 1982. Unlike police
data for the Chicago and New York areas, the Los Angeles metropolitan area
data were complete. Therefore, the Los Angeles area data were obtained
directly from UCR records.*** Police data for each county and year were
gathered from different sources for each metropolitan area. Population data
for each county and year were obtained from the Census Bureau so that
standardized rates could be used for comparisons.
In each metropolitan area, police-based crime rates rely on summaries
from multiple police departments and jurisdictions. As a result, it is not
possible to draw conclusions about the reporting practices of any
particular police department within the metropolitan area. Nonetheless,
it is possible to illustrate the degree of correspondence between the two
data series by comparing the crime rates based on police department
records to those estimated by the survey.
Nature of the comparisons
Three sets of estimates are provided for each crime type, year, and
metropolitan area. The first set of estimates, based on NCVS data, is
designated "NCVS Crime Rates." They consist of the burglary, robbery,
and aggravated assault victimization rates regardless of whether the
incident was reported to the police.***Footnote 7: Because the NCVS is
a household-based survey, it includes residential burglaries but not
commercial burglaries. The UCR data that were available to us included
both residential and commercial burglaries. Because we were unable to
determine how many of the police recorded burglaries were against
commercial establishments in each county and year, the UCR burglary
rates are expected to be higher than the NCVS reported burglary rates.
Also, unlike the NCVS burglary rate which is typically based on the
number of households, the UCR burglary rate is measured by taking the
total number of burglaries known to the police and dividing by the total
number of persons. To make the NCVS and UCR burglary rates as comparable as
possible, the NCVS rates were estimated using persons age 12 or over in the
denominator. In addition, it was not possible to determine how many of the
police recorded robberies and aggravated assaults were against persons under
age 12 (incidents excluded from the NCVS because persons under age 12 are
not interviewed). As a result, the NCVS robbery and aggravated assault rates
were created by dividing the number of victimizations by the population age
12 or over, while the UCR rates were created by dividing the total number of
offenses known divided by the total population for each county and year. UCR
rates based on the total population age 12 or over in the denominator also
were calculated to check the sensitivity of the findings to differences in
population coverage. Of course, the UCR rates increased when the denominator
was restricted to the population age 12 or over. However, the substantive
conclusions reported here were similar regardless of which denominator was
used for the UCR and NCVS rates.*** The second set of estimates, also based
on NCVS data, is the victimization rates based on incidents that victims
said were reported to the police. These estimates are referred to as "NCVS
Reported Crime Rates." The third set of estimates, based on police records,
consists of the UCR crime rates for each metropolitan area. These estimates
are referred to as "UCR Crime Rates."
For each metropolitan area and crime type, the NCVS Crime Rates are compared
with the NCVS Reported Crime Rates to assess whether levels of reporting
crime to the police have changed appreciably.***Footnote 8: Significant
changes were made to the methodology of the NCVS in 1992. To make the NCVS
rates comparable before and after 1992, the earlier rates were weighted by
their crime specific adjustment factors. These weights were derived from
assessments of how national estimates changed following a phase-in of
the new methodology. There is little reason to suspect that the effects of
the new methodology varied across these three metropolitan areas. For
more information on the weighting of crimes, see Kindermann, C., Lynch,
J., and Cantor, D. (1997), Effects of the Redesign on Victimization
Estimates, Bureau of Justice Statistics, NCJ 164381.*** The NCVS
Reported Crime Rates are compared to the UCR Crime Rates to ascertain the
correspondence between police data and victim reports for each metropolitan
area.
Burglary
New York Metropolitan Area
For the core counties of the New York metropolitan area, both police and
survey data agree that burglary declined from 1980 to 1998 (figure 1).
And as expected, the total NCVS burglary rate was higher than the UCR
burglary rate. According to New York area victims, roughly 61% of
burglaries were reported to the police over these two decades. The gap
between the NCVS burglary rates and the NCVS reported burglary rates
appears to have diminished somewhat in the New York metropolitan
area, suggesting an increase in reporting to the police.***Footnote 9: The
statistical limitations associated with the size of the metropolitan area
sample do not permit one to conclude that this change is statistically
significant. Statements about differences between the UCR crime rates
and the NCVS crime reported to police rates are based on the point
estimates shown in the figures and not strictly on significance testing. The
reason for this is that even though 3-year moving averages are used for
the NCVS rates, the 95% confidence intervals around those averages are, at a
minimum, plus or minus 4 per 1,000. Thus, very few of the annual differences
between a UCR rate and an NCVS reported to police rate would be statistically
significant. The purpose of these analyses is not to determine the specific
years in which the two rates are or are not statistically significant for
each crime type and metropolitan core county area, but to show the broader
patterns of correspondence between police data and victim survey reports.***
Throughout the 1980's and 1990's, the NCVS reported burglary rate was
similar to the UCR burglary rate. The correspondence in these two trends
indicates that the UCR burglary data for the New York metropolitan area
closely match both the levels and trends indicated by the victim survey
data.
Chicago Metropolitan Area
Police and survey estimates for burglary in the Chicago metropolitan
area agree that there was a decline in burglary throughout the 1980's
and 1990's. The NCVS burglary rate was higher than the UCR rate,
with victims in the Chicago area stating that 52% of burglaries were
reported to the police over this period. The gap between the NCVS
burglary rates and the NCVS reported burglary rates was somewhat
reduced later in the series, suggesting that there may have been an
increase in reporting to the police over these two decades.
In the Chicago metropolitan area, the NCVS reported burglary rate is
somewhat higher than the UCR burglary rate during the early years of the
time series. In later years, the NCVS reported burglary rate and the UCR
burglary rate corresponded more closely. Although long-term trends in
the victim and police data indicate a general decline in burglaries
reported to police, the decline appears greater in in the NCVS data than
in the Chicago metropolitan area police data.
Los Angeles Metropolitan Area
In the Los Angeles metropolitan region, police and survey data agree that
the burglary rate declined throughout much of the 1980's and 1990's. The
exception to the decline appeared in the late 1980's when the NCVS
rates suggested an increase in residential burglary victimization. The
decline in burglary in the Los Angeles region appeared larger than the
declines in the New York and Chicago areas because the survey based
rates in Los Angeles were higher in the earlier years of the time series.
According to victims, the level of reporting burglary to the police averaged
50% over the two decades, with no apparent change in the level at which
residential burglary was reported to the police.
Throughout much of the 1980's and 1990's, the NCVS reported burglary rate
was similar to the UCR burglary rate in the Los Angeles metropolitan area.
Since the early 1990's, the two data series have shown similar short and
long-term trends in burglary victimization.
Robbery
Unlike residential burglary, robbery can take place away from home. This
fact makes comparisons of UCR and NCVS robbery data more complex.
If a nonresident, such as a tourist or commuter, is victimized by robbery
while in the metropolitan area, the crime (if reported) is likely to be
reported to the police department with jurisdiction in the area where the
incident occurred. This means that UCR robbery counts for metropolitan
areas include crimes committed against nonresidents. NCVS robbery
counts, on the other hand, are based only on interviews with persons who
reside in the metropolitan core county areas. If UCR robbery rates for the
New York, Chicago, and Los Angeles areas contain many incidents against
persons who live outside these counties, they will be higher than
the local NCVS robbery rates.***Footnote 10: UCR robbery rates also
will be higher than NCVS robbery rates if police robbery data include
many incidents against persons who are not part of households (for
example, homeless persons). Such persons are ineligible to participate
in household-based surveys.***
Alternatively, if many of the robberies against metropolitan area residents
took place while they were outside of the core counties of their
metropolitan areas, the NCVS estimates could be higher than UCR
estimates. The NCVS counts do not easily distinguish victimizations that
occurred inside the metropolitan core county area from those that
occurred outside. Little evidence indicates which of the above concerns
is more problematic. To resolve the issue would require additional
information about the residence of each victim in UCR records and
location information for each incident in the NCVS reports. The
UCR-NCVS correspondence in robbery will reflect in part, the extent to
which these two concerns are relatively equal.
New York Metropolitan Area
Police and victim survey data for the New York metropolitan area agree
that robbery rates have generally declined over the past two decades
(figure 4). As expected, NCVS robbery rates were higher than UCR rates,
but both exhibit similar long-term trends. On average, about 53% of
robberies that occurred to residents were reported to the police, with no
statistically significant changes in reporting between the early and later
portions of the time series. Nonetheless, the NCVS data suggest a
decrease in the reporting of robbery to the police in the New York
metropolitan area from approximately 1989 to 1994.
From the mid-1980's until the mid-1990's, annual UCR robbery rates
were higher than NCVS reported robbery rates. Given the limitations
associated with the size of the sample, the annual differences were not
large enough to be statistically significant. Even so, this difference in
robbery rates may be important. If one assumes that the reliability of the
UCR and NCVS robbery rates did not change during this time period, the
higher UCR rates may have reflected a relatively higher occurrence of
robberies against nonresidents of the New York metropolitan area during
these years. The higher UCR rate might also indicate a relatively greater
increase in robbery against persons not captured in the NCVS sample,
such as homeless persons. If crimes against such groups increased at
rates higher than it did among others, UCR robbery rates could be higher
than NCVS reported robbery rates.
Chicago Metropolitan Area
Both police and victim survey data for the Chicago metropolitan area
suggest that robbery rates were lower in the late 1990's compared to the
early 1980's. Both data series show that the declines in the Chicago area
were relatively smaller than in the New York area during this same time
period. Over these two decades, the average level of robbery reporting
among residents was 56%, and there appears to have been relatively
little change in reporting.
As in the New York metropolitan area, Chicago area UCR robbery rates
were somewhat higher than NCVS reported robbery rates in several
years. These differences were not large enough to be found statistically
significant. After 1984 the short and long-term trends in NCVS reported
robbery rates and UCR robbery rates generally corresponded, although
the police data on robbery peaked and began to decrease about 2 years
earlier than the survey data.
Los Angeles Metropolitan Area
In the Los Angeles metropolitan area, robbery rates based on police and
victim survey data were lower in the late 1990's compared to the early
1980's. UCR and NCVS data agree that Los Angeles area robbery rates
declined from the mid-to late-1990's. The gap between NCVS robbery
rates and NCVS reported robbery rates changed little in the Los Angeles
area during the 1980's and 1990's. Roughly 49% of all robberies against
residents were reported to the police during these two decades.
Annual UCR robbery rates and NCVS reported robbery rates were very similar
throughout most of the 1980's and the latter half of the 1990's. As was
found in the New York and Chicago metropolitan areas, the Los Angeles area
UCR robbery rates were somewhat higher than NCVS reported robbery rates in
selected years of the series (roughly 1989 through 1993). Similarly, these
annual differences were not large enough to be statistically significant.
As noted earlier, the higher UCR robbery rate may reflect more robberies
against nonresidents or against persons not captured by the survey during
this time period.
Aggravated assault
Like robbery, comparisons of police and victim survey data for aggravated
assault involve unique complexities. Police data will include an unknown
number of crimes committed against nonresidents, and residents may become
victims of aggravated assault when they are outside of their metropolitan
area. Police data will also include an unknown number of crimes against
persons ineligible or unlikely to participate in the NCVS. But the
measurement of aggravated assault also is unique in that it is likely to
have been affected by broad scale changes in police response to domestic
assault incidents. Mandatory arrest policies have replaced informal
dispositions in many areas of the Nation. As a result, trends exhibited in
police data may not correspond closely with trends based on survey data, but
instead reflect changes in police handling of aggravated assault incidents.
New York Metropolitan Area
In the New York area, the NCVS data indicate that there were fluctuations in
aggravated assault levels, followed by a gradual decrease in the later 1990's.
Comparisons of NCVS aggravated assault rates and the NCVS reported aggravated
assault rates show no significant changes in the level at which these crimes
were reported to the police. About 56% of all aggravated assaults against
New York area residents were reported to the police. Police data for
aggravated assault suggest that there was a gradual increase in this crime
throughout the 1980's, followed by a gradual decline in the 1990's. Compared
to burglary and robbery, the correspondence between police and survey
estimates of aggravated assault levels and trends was lower. During much of
the 1980's and 1990's the police rate of aggravated assault was higher than
the NCVS reported rate. In several years the police-based rate of aggravated
assault in the New York metropolitan area was greater than the total NCVS
rate. Although the two series suggest different trends during some years,
there was greater similarity in the trends in the latter half of the 1990's.
Chicago Metropolitan Area
NCVS rates of aggravated assault in the Chicago metropolitan area show a
mixed set of trends. The survey data suggest that rates were at their
highest in the early 1980's and lowest in the later 1990's. The gap
between the NCVS aggravated assault rate and the NCVS reported aggravated
assault rate remained relatively consistent throughout the two decades.
Fifty-one percent of residents' aggravated assaults were reported to the
police during these years.
The correspondence between the police and survey estimates of aggravated
assault was lower in the Chicago area than the correspondence for the crimes
of burglary and robbery. Police rates of aggravated assault suggest increases
until the early 1990's, while NCVS rates suggest that the rates were highest
in the early 1980's. More fluctuations also were exhibited in the survey
estimates than in the UCR data. The lower degree of correspondence between
the NCVS aggravated assault rates and the UCR rates makes it difficult to
draw conclusions about more recent short-term trends in aggravated assault.
Los Angeles Metropolitan Area
In the Los Angeles area, the NCVS data exhibit no clear long-term trend
in the risk for aggravated assault victimization. The UCR rates, on the
other hand, suggest stability in the early 1980's, an increase in the later
1980's, and a steady decrease beginning around 1992. The gap between the NCVS
aggravated assault rate and the rate reported to police was steady, and the
average level of reporting among residents was approximately 50%.
Both police and victim survey data in the Los Angeles metropolitan area
agree that aggravated assault began to decrease gradually in the early
1990's. But for earlier years, the two series often suggested different
year-to-year changes in aggravated assault rates. Nonetheless, the UCR
rates were similar to the NCVS reported rates, indicating agreement
about the level of aggravated assault brought to the attention of the
police.
Conclusions
As noted earlier, local governments often are interested in assessing
levels or trends in crime, but they typically draw conclusions about crime
in their areas solely on the basis of police data. These analyses have
examined how police data compare to victim survey data for burglary,
robbery, and aggravated assault for the three largest metropolitan areas
in the Nation. For burglary and robbery, UCR crime rates were generally
similar to NCVS reported crime rates in the New York, Chicago, and Los
Angeles areas for 1980 through 1998. Police and victim survey data were
more likely to show discrepancies in levels and trends of aggravated
assault, a crime that is likely to have been affected by broader policy
changes in police handling of domestic violence incidents.
Even though UCR rates and NCVS reported rates often suggest different levels
and trends in aggravated assault, there are many instances in which the two
data series provide statistically similar annual estimates for this crime.
For the Los Angeles metropolitan area for example, annual differences between
the UCR rates and NCVS reported rates rarely were statistically significant.
And for the New York and Chicago areas, the UCR rates and NCVS reported rates
did not
differ significantly in many of the years. Statistical significance is a
function of both sample size and the magnitude of the difference between the
NCVS reported rate and the UCR rate. Given the relative rarity of aggravated
assault and the sample size limitations noted earlier, it is not surprising
that few statistically significant differences are found. Nonetheless, the
differences between some of the UCR and NCVS annual estimates of aggravated
assault provide important information about the sensitivity of these
estimates to methodological differences between the two sources of data.
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U.S. Department of Justice
Office of Justice Programs
Bureau of Justice Statistics
Lawrence A. Greenfeld
Director
Janet L. Lauritsen, Professor, University of Missouri-St.
Louis, and Robin J. Schaum, University of Missouri-St. Louis,
wrote this report. The U.S. Census Bureau, in cooperation
with BJS, produced the data for the analyses presented.
Lawrence Greenfeld, Marshall DeBerry, Matt Durose, Patrick
Langan, and Michael Rand at BJS and Marilyn Monahan at the
Census Bureau assisted.
Professor Lauritsen was a Visiting Fellow at BJS and produced
this report under cooperative agreement 2002-BJ-CX-0002.
Findings and conclusions reported here are those of the
authors and do not necessarily reflect the official position
or policies of the U.S. Department of Justice and the Bureau
of Justice Statistics.
Address all correspondence to Professor Lauritsen at Department
of Criminology and Criminal Justice, University of Missouri-St.
Louis, 1 University Blvd., St. Louis, MO 63121, or
Janet_Lauritsen@umsl.edu.
February 2005, NCJ 208075
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02/24/05 ih