by Michael D. Maltz 

Department of Criminal Justice 

University of Illinois at Chicago 

and 

Visiting Fellow, Bureau of Justice Statistics 

This paper is based on a Workshop 

on Uniform Crime Reporting Imputation 

on April 24-25, 1997,

sponsored by the 

Bureau of Justice Statistics 

and the 

Federal Bureau of Investigation 

Uniform Crime Reporting Program

Summary

Crime in the United States (CIUS), published annually by the FBI, is a compilation of the Uniform Crime

Reports (UCR) provided by over 18,000 policing

jurisdictions. It represents one of the two primary

sources of data about crime in the United States, the

National Crime Victimization Survey (NCVS) being

the other. While the NCVS is a very reliable 

indicator of national trends in crime, it is based on a

survey of under 50,000 households and thus cannot

provide local information on crime, which is provided

by the UCR and CIUS. [For a thorough understanding of the differences between the two statistical 

series, see Biderman and Lynch's (1991) Understanding Crime Incidence Statistics: Why the 

UCR diverges from the NCS.1

 A briefer explanation

can be found in The Nation's Two Crime Measures,

found at

http://www.ojp.usdoj.gov/bjs/abstract/ntmc.htm

and included annually in CIUS.]

Not only does CIUS provide local information about

crime incidence, it also compiles arrest data from

these jurisdictions; these data permit us to form a

picture of who is committing crime (or at least, who

is arrested for committing crime).

Reporting to the FBI remains for many jurisdictions 

a voluntary activity; although many States now

mandate that agencies report crime and arrest data

to them (which they then forward to the FBI), even 

in those States local agencies do not always comply.

1

The NCS, or National Crime Survey, was the predecessor to the NCVS. 

U.S. Department of Justice 

Office of Justice Programs

Bureau of Justice Statistics

Executive Summary

Bridging Gaps in 

Police Crime Data

A Discussion Paper from the BJS Fellows Program

July 1999, NCJ 177615 
Moreover, despite the efforts of the FBI to maintain

their quality, there are many gaps in the data that

make their use questionable. While this has had limited impact in the past, the fact that the UCR data

have, for the first time, been used to allocate Federal funds brings issues about data quality to center

stage. 

In addition, the FBI is moving to implement an 

improved crime and arrest reporting system, the 

National Incident-Based Reporting System (NIBRS),

to replace the summary UCR program. It is hoped

that the study of deficiencies in UCR data will be of

use in planning toward the full implementation of

NIBRS.

This report describes the history of the UCR system

and the data problems that it deals with in reporting

about crime, arrests, and homicide. It describes the 

procedures used by the FBI to fill in gaps in the 

data, when they exist, and makes suggestions 

about how they might be improved.

A note of thanks from Michael Maltz

I began work on this project because, although I had

been using the UCR for many years, I had never understood all of its intricacies and felt somewhat embarrassed to ask simple questions about why certain

procedures were used, because obviously everyone

else knew. It turned out, however, that most people

seemed to be as much in the dark as I was, perhaps

about different aspects of the UCR, and during this

project we began to share our knowledge, each of

us having an understanding of different aspects of

the data collection and analysis process. This report

is, then, more of a collaboration than a singleauthored effort, a kind of "open source" presentation

of our collective knowledge.

The information contained herein is based on a

2-day meeting held over 2 years ago; analyses of

UCR data conducted since then; and conversations,

letters, faxes, and emails between me and a number

of colleagues. In particular, I wish to acknowledge

the comments and advice of the folllowing:

 From BJS  Jan Chaiken, Larry Greenfeld, 

Charles Kindermann, Pat Langan, Sue Lindgren,

Don Manson, Mona Rantala, Steve Smith, Paul

White, and Marianne Zawitz

 From the FBI  Yoshio Akiyama, Bennie Brewer,

Ken Candell, Carlos Davis, Gil Gee, Antonio Hwang,

John Jarvis, Dawn Kording, Vicki Major, Jim Nolan,

Sharon Propheter, and Maryvictoria Pyne

 From the research community  Dan Bibel,

Becky Block, Roland Chilton, Chris Dunn, Bob

Flewelling, Jamie Fox, Jim Lynch, Mike Maxfield,

and Howard Snyder.

In addition, I wish to thank the UCR program

personnel from the 50 States with whom my 

research assistants (Leanne Brecklin, University of

Illinois at Chicago; Chris Kenaszchuk, University of

Maryland; and Todd Minton, BJS) and I corresponded and spoke. I received cooperation from

virtually every State in putting together this report; I

hope that the end result is of use to them and to others who deal with crime statistics.

This report was written while I was a Visiting Fellow

at the Bureau of Justice Statistics, and completed

while I was on sabbatical from the University of 

Illinois at Chicago. While I greatly appreciate the

help I received from BJS, FBI, and State officials,

they should not be held responsible for any errors

in this report, and the opinions, conclusions, and

recommendations expressed herein are my own 

and should not be construed as the policy of any 

of these organizations. 

Bridging Gaps in Police Crime Data 2 Executive Summary
Contents

(from the full 76-page report)

I. Introduction . . . .......................... 1

Why We Need to Look at the UCR . . . . . . 2

The Information-Gathering Process . . . . . 3

Report Organization . . . .............. 3

II. UCR History and Coverage . . . ............. 4

State-Level Reporting . . . ............. 4

Comparing Crime Data . . . ............ 4

Coverage Gaps and Imputation . . . ..... 5

The UCR and Funding Decisions . . . .... 7

The UCR and Electronic Access . . . ..... 9

Use of Sub-National UCR Data . . . . . . . 10

The UCR and NIBRS . . . . . . . . . . . . . . . 11

III. Incomplete Crime Data . . . . . . . . . . . . . . . . . 16

Error Checking . . . . . . . . . . . . . . . . . . . . . 16

Reasons for Incomplete Reporting . . . . . 16

IV. Incomplete Arrest Data . . . . . . . . . . . . . . . . . 18

V. Processing and Publishing the Crime Data . . 21

Publishing the UCR . . . . . . . . . . . . . . . . . 21

Archiving the UCR Data File . . . . . . . . . 22

VI. Procedures Used for Imputing Crime Data . . 23

FBI Imputation Procedures for Crime . . . 23

NACJD Imputation Procedure . . . . . . . . 23

Imputation Procedures for Arrests . . . . . . 24

Imputation and "Zero-Population"

 Agencies . . . . . . . . . . . . . . . . . . . . . . . 24

Updating UCR Files . . . . . . . . . . . . . . . . . 25

VII. Inaccuracies Produced by the Imputation 

Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Incomplete-Reporting Agencies . . . . . . . . 26

Non-Reporting Agencies . . . . . . . . . . . . . 26

"Zero-Population" Agencies . . . . . . . . . . . 26

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . 27

VIII. Suggested Alternative Imputation 

Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Incomplete Reporting Agencies . . . . . . . . 28

Non-Reporting Agencies . . . . . . . . . . . . . 30

Zero-Population Agencies . . . . . . . . . . . . 30

 

IX. Supplementary Homicide Reports . . . . . . . . 31

Uses of the SHR . . . . . . . . . . . . . . . . . . . . 31

Incomplete Provision of SHR Data 

 by Police Departments . . . . . . . . . . . . . 32

Updating SHR Files . . . . . . . . . . . . . . . . . 33

Availability of SHR Data Sets . . . . . . . . . . 34

SHR Imputation . . . . . . . . . . . . . . . . . . . . . 35

Weighting the Victim File . . . . . . . . . . . . . . 35

Weighting the Offender File . . . . . . . . . . . . 36

Problems with This SHR Imputation

 Procedure . . . . . . . . . . . . . . . . . . . . . . . . 37

Suggested Alternative SHR Imputation 

 Procedure . . . . . . . . . . . . . . . . . . . . . . . . 38

X. Conclusions and Recommendations . . . . . . . 39

Appendix A. Persons Attending the Workshop 

on UCR Imputation Procedures . . . . . . . . . . . . . . 41

Appendix B. State On-Line Publication 

of Crime Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Appendix C. Extent of UCR Data 

Coverage, Alabama-Wyoming, 1958-97 . . . . . . . 43

Appendix D. Characteristics of State UCR 

Collection Programs . . . . . . . . . . . . . . . . . . . . . . . 60

Appendix E. Missing Data in UCR Files Used 

for the 1996 LLEBG Formula Calculations . . . . 62

Background . . . . . . . . . . . . . . . . . . . . . . . . 62

Extent of Missing Data, by State . . . . . . . 62

Characteristics of Agencies with Less 

 than 36 Months of Violent Crime Data 62

Agencies with 0 Months Data . . . . . . . . . . 62

Jurisdictions with between 1 and 

 35 Months of Data . . . . . . . . . . . . . . . . 63

Impact of Incomplete Data . . . . . . . . . . . . 63

Addendum on "Zeropop" Agencies . . . . . . 64

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

 Bridging Gaps in Police Crime Data 3 Executive Summary 
The Uniform Crime Reporting Program (UCR)

1

 of the Federal Bureau of

Investigation (FBI) has been collecting crime

and arrest data from police departments

throughout the United States since 1930. The

data are published in the annual report, Crime

in the United States (CIUS), and represent

one of the more widely used sources of

longitudinal data in the social sciences. The

UCR is based on monthly summary reports of

crimes known to the police and arrests made

by the police, that are provided to the FBI by

more than 18,000 police agencies in the

United States and its territories.2

The FBI office that deals with the UCR

is the Program Support Section (PSS), a

section of the Criminal Justice Information

Services (CJIS) Division. Five of the eight

units within PSS are concerned with various

aspects of CIUS: 

 ̆ The Statistical Unit collects, checks,

and manages the data coming in from

the police agencies.

 ̆ The Communications Unit is involved

in publications and data

dissemination.

 ̆ The Education and Training Services

provides training to local agencies in

UCR data collection procedures.

 ̆ The Crime Analysis Research and

Development analyzes data and

develops specifications for new

methods of presenting the data.

 ̆ The CJIS Audit Unit performs quality

assurance reviews to maintain the

quality of the UCR.

The UCR includes a Crime Index, a

count of certain specific crimes occurring over

the past year in each jurisdiction. These are

called “Index crimes,” and, listed in order of

their presumptive seriousness, are murder

and nonnegligent manslaughter, forcible rape,

robbery, aggravated assault, burglary,

larceny-theft, and motor vehicle theft. 

Arson was added to the Crime Index

in 1979 although it is not as likely as the other

Index crimes to be reported to the police,

because arsons are often categorized as “fires

of suspicious origin.” Except for arson, these

particular crimes were chosen because they

were frequent, generally serious in nature, and

most likely to be reported to the police;

victims, their relatives, and/or bystanders who

witness the incident are likely to know that

incidents of those types are criminal in nature

and are likely to report them.

Although the UCR has some

limitations (indeed, the aim of this report is to

address some of them), even these limitations

provide important information. For example,

incomplete citizen reporting to the police of

certain types of crimes has been used as an

indicator of a number of police-related factors:

how the relationship between offender and

victim affects citizen reporting of crime; the

extent to which citizens trust the police; and

the effect of police policies and problems on

reporting behavior. Yet the public is generally

unaware that the UCR system is essentially a

voluntary system; there is no federal

legislation that requires states or local

jurisdictions to report their crime data to the

FBI.

The voluntary nature of the UCR, of

course, affects the accuracy and completeness of the data. Although the FBI devotes a

great deal of attention to the quality of the data

it publishes in CIUS, it cannot mandate

agencies to provide data on time (or at all). As

a consequence, the FBI must deal with

problems of missing or late data, and has

developed a mechanism to account for these

gaps: it imputes (or estimates) data where

gaps exist, which limits the accuracy of the

crime statistics published in CIUS.

I. Introduction

Bridging Gaps 4 in Police Crime Data

2

Police agencies also report on other topics to the FBI, including hate crimes, personnel

statistics, and law enforcement officers killed and assaulted. These topics are not covered in this report.

1

The first mention of an acronym in this report is printed in bold. Also see Glossary, page 72.
Why We Need to Look at the UCR

Despite these problems with the data,

adjustments for missing data have not been of

major consequence in the past, since the

primary purpose of the data was to present

national and State trends & and the

adjustments were adequate for this purpose.

Researchers, police administrators, and some

journalists are aware of the limitations of the

UCR, but it mattered little to others outside the

field. However, in the recent past four changes

were made in the environment in which the

UCR data are being employed:

 ̆ UCR data are being used to allocate

Federal funds.

 ̆ The data are now instantly accessible

on the Internet.

 ̆ Because of the greater accessibility 

of the data, researchers are

increasingly analyzing UCR statistics

at sub-national levels, but the results

of their analyses may be suspect

because of the way missing data are

handled.

 ̆ A new reporting system (the National

Incident-Based Reporting System, or

NIBRS) now being implemented to

augment – and ultimately replace &

the UCR, will increase the amount of

data collected on each crime.

Thus, the collection, analysis, and

publication of crime data are now occurring in

a new environment, due to changes in

legislation, changes in the ease of access by

citizens and researchers to the data, and

changes in crime reporting. This means that

the FBI’s imputation procedures, which were

adequate for handling many of the

weaknesses in the current data collection

system, may have to be revised.

Toward this end, a Workshop on UCR

Imputation Procedures was held in

Washington, DC, April 24-25, 1997, and

attended by key personnel from the FBI and

the Bureau of Justice Statistics (BJS), as well

as by researchers familiar with UCR data and

their problems. The list of attendees is given 

in Appendix A of the full report. Just prior 

to the workshop the FBI had moved the

Program Support Section to Clarksburg, West

Virginia. The move resulted in a turnover of

personnel and equipment. The workshop thus

came at an opportune time for the FBI, which

recognizes the need to update the procedures

it has been using for 40 years & when the

UCR had its last major revision (FBI, 1958). 

The workshop provided an opportunity

for statisticians and researchers from both of

these Federal agencies and from the user

community to discuss ways of improving UCR

data collection and estimation procedures.

The goal of the workshop was to recommend

new ways to ensure that the American public

is provided with the best possible policecollected information related to crime and

criminality, and to move toward that end in the

most expeditious and feasible way possible.

This report is based on the findings and

discussions from that workshop.

Issues relating to standard UCR data

(i.e., crime counts, arrests) were not the only

topics addressed at the workshop. Attention

was also devoted to the Supplementary

Homicide Reports (SHR), forms filled out by

police departments that provide a more

detailed description of each homicide than just

the raw statistics of number of homicides. The

workshop explored how these data could be

made more useful, and this report discusses

those findings as well.

Issues related to Federal crime data

are not included in this report. Thus, the

accuracy or completeness of the statistics of

crimes committed on Indian reservations,

military installations, and national parks are for

the most part excluded. 

This report also includes information

gathered from State criminal justice agency

personnel and data analyses subsequent to

the workshop. 

Bridging Gaps 5 in Police Crime Data
The Information-Gathering Process

The information contained in this

report has come from a variety of sources.

Much of it is undocumented, and falls more in

the category of "lore" than "information." The

voluntary nature of the UCR system means

that different standards and procedures have

been used in different States despite the

name given to the data system – the Uniform

Crime Reports are far from uniform. Some of

the material included herein is based on

informal conversations with FBI and BJS

personnel and State officials who use or

collect the data, and some of their statements

about the UCR (or my interpretations of what

they meant) may be in error. Although I have

tried to verify all statements, some errors may

have slipped through. Should a reader find

mistakes in this report, please notify me

(mikem@uic. edu), and corrections will be

added to an errata sheet that will be posted 

on the BJS website.

It seems that every decade or so I

look into the intricacies of crime data (Maltz,

[1972] 1999; 1984: 141) and find the following

caution about official statistics from Josiah

Stamp (1929: 258) applicable:

The individual source of the

statistics may easily be the weakest

link. Harold Cox tells a story of his

life as a young man in India. He

quoted some statistics to a Judge,

an Englishman, and a very good

fellow. His friend said, "Cox, when

you are a bit older, you will not

quote Indian statistics with that

assurance. The Government are

very keen on amassing statistics –

they collect them, add them, raise

them to the nth power, take the

cube root and prepare wonderful

diagrams. But what you must never

forget is that every one of these

figures comes in the first place

from the chowty dar [village

watchman], who just puts down

what he damn pleases."

While strides have been made in

improving the coverage and accuracy of

police-reported crime data (in India as well as

in this country), there is still need for a great

deal of improvement. My hope is that this

report helps to realize this goal.

Report Organization

The organization of this report is as

follows: The next section gives a brief

summary of how the coverage of the UCR has

increased over the past few decades, both in

terms of population covered and State

collection efforts. Section III describes the

reasons for incomplete crime data and

Section IV problems with arrest data. Section

V documents the steps necessary to verify

and publish CIUS. The imputation procedures

used by the FBI to account for these gaps are

described in Section VI, and the problems with

these imputation procedures in Section VII.

Some suggested changes in the imputation

procedures are described in Section VIII.

Issues related to the SHR data are addressed

in Section IX. Conclusions and recommendations are found in Section X. 

Five appendixes are included:

Appendix A lists the attendees at the BJS/FBI

workshop. Appendix B is a compendium of

crime-related data available on the Internet

from State agencies. The crime reporting

history of each State is charted in Appendix C.

Appendix D lists some of the characteristics of

State UCR collection programs. Appendix E,

written by Sue Lindgren of BJS, describes the

procedures used to account for missing data

in calculating the Local Law Enforcement

Block Grant funding for each jurisdiction.

Bridging Gaps 6 in Police Crime Data
Bridging Gaps 7 in Police Crime Data

*Three States ceased submitting State-level data in the 1980’s.

States that had problems with some or all of the submitted data

States reporting UCR data to the FBI

 1969 1975 1980 1985 1990 1995 

Wisconsin 

Vermont

Rhode Island

Pennsylvania

New Jersey

Nebraska

Montana

California

Minnesota

Kentucky

Florida

West Virginia

Delaware

North Carolina

Michigan

South Carolina

Oregon

Oklahoma

New Mexico*

Nevada

Maine

Illinois

Idaho

Arkansas

Virginia

Tennessee*

New York

Maryland

Louisiana

Kansas

Iowa

Hawaii

Georgia

Arizona

Texas

Ohio*

Colorado

Alabama

Wyoming

New Hampshire

Massachusetts

Connecticut

North Dakota

Washington

District of Columbia

South Dakota

Utah

Missouri

Mississippi

Indiana

Alaska

Figure 4. State-Level Reporting of UCR Data to the FBI

Sources: CIUS, 1969-96, and responses from State officials by letter, email, and telephone.
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Bridging Gaps in Police Crime Data 

A Discussion Paper from the BJS Fellows Program