Uniform Crime Reporting Program Resource Guide

Uniform Crime Reports (UCR) serve as periodic nationwide assessments of reported crimes not available elsewhere in the criminal justice system. By 1985, there were approximately 17,000 law enforcement agencies contributing reports either directly or through their state reporting programs. By 1998, the number of agencies was over 18,500. More information about the development of the UCR Program can be found on the FBI website.

Using the Resource Guide

NACJD, a part of the Inter-University Consortium for Political and Social Research (ICPSR) at the University of Michigan, designed this Resource Guide for World Wide Web users to learn about the FBI's Uniform Crime Reporting Program and to connect to other related information sources.

With this guide, first time users or experienced analysts can:

Types of UCR Data Available at NACJD

Agency-Level UCR Data

The agency-level data, where the unit of analysis is the police agency (or incident for Supplementary Homicide Reports and Hate Crime), comprises seven data files per year and contain information on:

  1. Offenses Known and Clearances by Arrest data files include monthly data on the number of Crime Index offenses reported and the number of offenses cleared by arrest or other means. The counts include all reports of Index Crimes (excluding arson) received from victims, officers who discovered infractions, or other sources.
  2. Property Stolen and Recovered data are collected on a monthly basis by all UCR contributing agencies. These data, aggregated at the agency-level, report on the nature of the crime, the monetary value of the property stolen, and the type of property stolen. Similar information regarding recovered property is also included in the data.
  3. Supplementary Homicide Reports (SHR) provide incident-based information on criminal homicides. The data, provided monthly by UCR agencies, contain information describing the victim(s) of the homicide, the offender(s), the relationship between victim and offender, the weapon used, and the circumstance of the incident.
  4. Police Employee (LEOKA) Data provide information about Law Enforcement Officers Killed or Assaulted (hence the acronym, LEOKA) in the line of duty. The variables created from the LEOKA forms provide in-depth information on the circumstances surrounding killings or assaults, including type of call answered, type of weapon used, and type of patrol the officers were on.
  5. Hate Crime Data contain information about crimes that manifest evidence of prejudice based on race, religion, sexual orientation, ethnicity, and mental or physical disabilities. The FBI began to collect these data under the Hate Crime Statistics Act of 1990. Information contained in the data include number of victims and offenders involved in each hate crime incident, type of victims, bias motivation, offense type, and location type.
  6. Arrests by Age, Sex, and Race monthly reports provide information on the number of arrests reported to the UCR Program each year by police agencies in the United States. These arrest reports provide data on 43 offenses including violent crime, drug use, gambling, and larceny. The data received by ICPSR were structured as a hierarchical file containing (per reporting police agency) an agency header record, and 1 to 12 monthly header reports, and 1 to 43 detailed offense records containing the counts of arrests by age, sex, and race for a particular offense. ICPSR restructured the original data to logical record length format with the agency header record variables copied onto the detailed records
  7. Arrests by Age, Sex, and Race, Summarized Yearly provide information on the number of arrests reported to the Federal Bureau of Investigation's Uniform Crime Reporting (UCR) Program each year by police agencies in the United States. These arrest reports provide data on 43 offenses including violent crime, drug use, gambling, and larceny. The data received by ICPSR were structured as a hierarchical file containing, per reporting police agency: an agency header record, and 1 to 43 detail offense records containing the counts of arrests by age, sex, and race for a particular offense. ICPSR restructured the original data to logical record length format with the agency header record variables copied onto the detail records. Consequently, each record contains arrest counts for a particular agency-offense.
  8. Arson includes monthly data on the number of arson offenses reported and the number of offenses cleared by arrest or other means. The counts include all reports of arson received from victims, officers who discovered infractions, or other sources.

UCR Agency-Level Data, 1975-Current

*Prior to 1998, all data save for Hate Crime data were merged into one study (ICPSR 9028).
**Hate Crime data are not available prior to 1992.

1966-1976 Data Collections

Earlier years of agency-level data, where the unit of analysis is the police agency, include one data file per year for the years 1966-1976 and contain the following information:

  1. Return A Monthly Return of Offenses Known to the Police
  2. Supplement I to Return A - Additional Analysis of Motor Vehicle Theft, Burglary, Robbery and Larceny
  3. Supplement II to Return A - Values of Stolen and Recovered Property

View UCR Agency-Level Data for 1966-1976 (has been merged into one study)

Incident-Level UCR Data

Incident-level data are collected through the National Incident-Based Reporting System (NIBRS) component of the UCR. NIBRS collects data on each single incident and arrest within 22 offense categories made up of 46 specific crimes called Group A offenses. For each of the offenses coming to the attention of law enforcement, specified types of facts about each crime are collected. In addition to the Group A offenses, there are 11 Group B offense categories for which only arrest data are reported. More information about this study can be found in the NIBRS Resource Guide.

County-Level UCR Data

The county-level Uniform Crime Reporting files contain only data on arrests and crimes reported, and are distributed annually as four separate data files:

  1. Arrests, All Ages
  2. Arrests, Adults
  3. Arrests, Juveniles
  4. Crimes Reported

Beginning in 1993, an Allocated Statewide Data file is also distributed for each part above. The Statewide data files provide the amount of data from statewide agencies allocated to each county based on the county's share of the states’ population. These Statewide data files can also be used to "back out" the statewide counts if only the county total is desired.

  1. Allocated Statewide Data for Arrests, All Ages
  2. Allocated Statewide Data for Arrests, Adults
  3. Allocated Statewide Data for Arrests, Juveniles
  4. Allocated Statewide Data for Crimes Reported

Study Design

County-level UCR files are created by NACJD based on agency records in a file obtained from the FBI that also provides aggregated county totals. NACJD imputes missing data and then aggregates the data to the county-level. Specific information about the imputation algorithm can be found in the codebooks for each year of the county-level files. A new imputation algorithm was implemented in 1994. Therefore, data files prior to 1994 are not necessarily comparable to the files from 1994 and onward. The new imputation algorithm more closely approximates the estimation procedures used by the FBI to adjust for incomplete or unreported data from individual law enforcement jurisdictions for their Crime in the United States publications. Users are strongly encouraged to carefully read the study documentation for each year before analyzing these data.

Two major changes to the UCR county-level files were implemented with the 1994 release data. A new imputation algorithm to adjust for incomplete reporting by individual law enforcement jurisdictions has been adopted. Also, a new Coverage Indicator has been created to provide users with a diagnostic measure of aggregated data quality in a particular county. These developments are described in greater detail below. The changes were instituted in response to comments from a number of users and after almost a year of discussions by UCR file users, the Uniform Crime Reports Unit of the Federal Bureau of Investigation, the Bureau of Justice Statistics, and the Inter-university Consortium for Political and Social Research.

These changes will result in a break in series from previous UCR county-level files. Data from earlier year files should not be compared to data from 1994 and subsequent years. Changes in procedures used to adjust for incomplete reporting at the ORI or jurisdiction level may be expected to have an impact on aggregates for counties in which some ORIs have not reported for all 12 months. However, the new adjustment procedures should result in county-level data that are less sensitive to changes between years in the extent of reporting by ORIs within a county. Consequently, data from 1994 forward should yield more accurate estimates for longitudinal analysis.

IMPUTATION PROCEDURES USED FOR 1994 UCR COUNTY-LEVEL FILES AND ONWARD: The data for any ORI reporting 12 months were used for county aggregation as submitted. Data for an ORI reporting 3 to 11 months were increased by a weight of [12/months reported]. For ORIs reporting 0 to 2 months, data for these ORIs were set to zero and then data were estimated using rates calculated from ORIs reporting 12 months of data located in the ORIs geographic stratum based on UCR Population Groups within their state. UCR Population Groups are defined as follows:

  1. Cities 250,000 and over
  2. Cities 100,000 - 249,999
  3. Cities 50,000 - 99,999
  4. Cities 25,000 - 49,999
  5. Cities 10,000 - 24,999
  6. Cities 2,500 - 9,999
  7. Cities under 2,500
  8. Non-MSA counties and non-MSA State Police
  9. MSA counties and MSA State Police

COVERAGE INDICATOR: For releases of UCR county-level files before 1994, data from jurisdictions reporting less than 6 months of data were not included in county totals in an effort to ensure cross-sectional data comparability and quality. With the new procedures to adjust for incomplete reporting, data will be provided for each active ORI that reports less than 12 months of data, whether through weighting of partial year data or substitution of a value based on population group and state. Instead of exercising an a priori judgment that 6 months of data is the minimum threshold for acceptable data quality, a new Coverage Indicator variable has been created that will allow users to set their own threshold for acceptable data quality and to include or exclude data based on the standards they set themselves. The Coverage Indicator variable represents the proportion of county data that is not imputed for a given year. The indicator ranges from 100, indicating that all ORIs in the county reported for 12 months in the year, to 0, indicating that all data in the county are based on estimates (as described above), not reported data. The Coverage Indicator is calculated as follows:

CIx = (1-(sum((ORIi pop/county pop)((12-months reported/12))))*100

CI = Coverage Indicator
x = county
i = ORI within county

Some ORIs do not have a population associated with their jurisdiction. These ORIs report for jurisdictions such as national parks, colleges and universities, toll bridges and tunnels, and most state police departments. As the coverage indicator is based on months of reporting and the population of each agency, this variable will not show estimation that did occur for statewide ORIs and for ORIs as listed above that do not have a population but reported 3 to 11 months of data. Conversely, the coverage indicator will indicate that estimation has occurred for ORIs with a population that reported 3 to 11 months of data even if the ORIs actually reported no crimes or arrests. Similarly, the coverage indicator will indicate that estimation had occurred for ORIs with a population that reported 0 to 2 months of data, even though no rate was calculated to estimate data because of the lack of ORIs in the agency's geographic stratum reporting 12 months of data. Finally, since data for ORIs that reported 0 to 2 months of information are set to zero, users should be aware that no estimation of data was possible for ORIs without a population that reported 0 to 2 months of data.

It should be emphasized that, while UCR staff were consulted in developing the new adjustment procedures, these UCR county-level files are not official FBI UCR releases and are being provided for research purposes. Users with questions regarding these UCR county-level data files can contact the National Archive of Criminal Justice Data at ICPSR.

ADDITIONAL NOTES: In the UCR county-level arrest files, the population and data for jurisdictions located in multiple counties are provided only in the county containing the largest population component of the jurisdiction. Counties containing smaller population components of multiple-county jurisdictions will contain no population or arrest data for these jurisdictions. Data in counties affected by one or more multiple-county jurisdictions are indicated by a multi-county jurisdiction flag variable. In the county-level crimes reported files, the population and crime data for jurisdictions located in multiple counties are provided by the UCR porportioned to each county (maximum of three) in which the jurisdiction is located.

Cities designated by the Census Bureau as independent cities are reported separately and have their own "county" codes. Some jurisdictions, such as state parks and some state police, provide data only on a statewide basis. In these cases, data are allocated to counties proportionate to their share of the total state population. State Police data for Vermont that were not reported within a county and the State Police data for Alaska are not allocated to the counties. These two State Police records are identified by the county code 999.

The original data from the FBI contains one record for New York City. Data from New York City are allocated into New York City's five counties on the basis of the proportion of the population in each county. For example, the population for Queens county is divided by the total population of New York City and the resulting proportion is multiplied with data from each of New York City's arrest and offense categories to apportion data to Queens county.

Variables

The three arrest parts contain identical variables: FIPS state and county codes, total county population of agencies reporting arrest data, number of agencies in the county, multi-county jurisdiction flag, coverage indicator, total number of arrests, total number arrests for Part I (index) crimes, total number of arrests for violent crimes, total number of arrests for property crimes, and arrest counts for each Part I and Part II crime.

The crimes reported part contains FIPS state and county codes, state population, total county population of agencies reporting arrests, county population of agencies reporting crimes, number of agencies in county reporting arrests, total number of agencies in county reporting crimes, coverage indicator, total crimes reported for Part I crimes not including arson (index), total crimes reported for Part I crimes including arson (modified index), and counts of crimes reported for each Part I crime.

Data Collection Notes

Users who are interested in the alogorithm used to prepare the county-level UCR data for the years 1977 to 1993 are encouraged to refer to the codebooks for the annual county-level data for a full description.

Comparing "CRIME IN THE UNITED STATES" TO ICPSR County-Level UCR Data:
"Crime in the United States" is a publication prepared by the FBI and provides estimations of national reported crime activity and arrest statistics from law enforcement agencies in the UCR Program. Users of this data collection prepared by ICPSR may not be able to match the statistics presented in "Crime in the United States" due to several factors:

  1. The UCR staff continue to update agency records when additions or corrections are received by the UCR Program. The FBI statistics presented in "Crime in the United States" are based on the data that the FBI has received prior to their established publication deadlines. The data used by ICPSR to prepare the UCR County-Level data may contain additions or corrections to the data submitted to the FBI after their publication deadline for producing "Crime in the United States."
  2. The new imputation algorithm that ICPSR implemented in 1994 approximates the estimation procedures that the FBI uses to adjust for incomplete or unreported data from individual law enforcement jurisdictions. Either limited or no crime or arrest data were available for some states in some years because these states are in the process of converting to the National Incident-Based Reporting System (NIBRS). For some tables in "Crime in the United States," the FBI provided estimated crime counts and arrest totals for each of these states. ICPSR algorithm estimates data for agencies reporting less than three months of data by calculating rates from agencies reporting 12 months of data located in the agency's geographic stratum within that state. Since data for these states were very limited or not present in the original data, estimates for the entire state could not be produced by ICPSR.
  3. Some tables in "Crime in the United States" were prepared using data only from agencies submitting complete reports for the 12 months for the year prior to the publication deadline. For ICPSR data collections, all law enforcement agency records present in the original FBI data were used in the aggregation to the county level. County records with a coverage indicator value of 100 contain only 12-month reporting agencies (see PDF codebooks for possible exceptions.) Agencies reporting 12 months of data within a county with a coverage indicator value less than 100 cannot be separately identified in this dataset aggregated at the county level.

Search for County-Level UCR data available from NACJD.

Online Analysis of UCR Data

Uniform Crime Reports County-Level Arrest and Offense Data from 1994 through 2001 (ICPSR 6669, 6850, 2389, 2764, 2910, 3167, 3451, 3721) are available for online analysis using NACJD's Online Survey Documentation and Analysis. Users are strongly encouraged to read the description of the county-level UCR Data before performing online analyses.

With the Online Survey Documentation and Analysis, users can perform online analyses on All Ages Arrest Data, Adult Arrest Variables, Juvenile Arrest Variables, and Crimes Reported Variables. Online data analysis is recommended for users who would like to search for variables of interest in a dataset, review frequencies or summary statistics of key variables to determine what further analyses are appropriate, review frequencies or summary statistics for missing data, produce simple summary statistics for reports, create statistical tables from raw data, and those who would like to create a subset of cases or variables from a particularly large colection to save time in downloading and space on a personal computer. Please see the Online Survey Documentation and Analysis for more information.