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Conversion of NIBRS Data to Summary Data

Conversion of NIBRS Data to Summary Data

Law enforcement agencies across the Nation began implementing incident-based reporting systems two decades ago. Currently, many agencies are either certified to report crime data through the National Incident-Based Reporting System (NIBRS) or are in the process of developing the NIBRS. With this limited amount of data, the FBI's Uniform Crime Reporting (UCR) Program publishes NIBRS monographs and special studies to demonstrate the utility and richness of the NIBRS data. However, until the FBI's UCR Program receives the preponderance of data via the NIBRS, the FBI will continue to report national crime statistics in the traditional Summary format. During this period of transition, the FBI converts statistics submitted by agencies that report crime data via the NIBRS to the traditional Summary format and incorporates them into the national crime database. This document details the procedures the FBI follows when converting NIBRS data to Summary data as well as how it derives some statistics for the Law Enforcement Officers Killed and Assaulted (LEOKA) Program. Form numbers from the Office of Management and Budget (OMB) follow each form name.

The conversion procedures illustrated in this document use the 57 NIBRS data elements and their respective data values to convert NIBRS data into the traditional Summary data and LEOKA data. (See NIBRS Volume 1: Data Collection Guidelines [August 2000] and The NIBRS Addendum for Submitting LEOKA Data [October 2002] for an explanation of data elements and data values.) For each agency that reports to the UCR Program via the NIBRS (according to NIBRS Volume 2: Data Submission Specifications [2001]), the FBI stores the data in a flat file (NIBRS Flat File Record Description), then converts the NIBRS data for each flat file record into the conventional format of the UCR Summary forms and the LEOKA form for publication purposes. (See the Uniform Crime Reporting Handbook, Summary edition, revised 2004 [UCR Handbook, 2004], for samples of each form.) This document is based on the storage format of the NIBRS Flat File Yearly Record Descriptions. Once converted from NIBRS submissions, the Summary data are available as printouts to state and local agencies for review. The Summary printouts contain incident reports that are aggregated by offenses, arrests, property types and values, clearances, and details of homicides.

When converting NIBRS data to Summary data, the FBI takes only one offense from each NIBRS incident. The FBI bases its selection on the Hierarchy Rule, which ranks traditional Part I offenses from high to low as follows:

NIBRS offense code:

    09A - Murder and Nonnegligent Manslaughter
    09B - Negligent Manslaughter
    11A - Forcible Rape
    120 - Robbery
    13A - Aggravated Assault
    220 - Burglary/Breaking and Entering
    23A - 23H - Larceny-theft
    240 - Motor Vehicle Theft
    200 - Arson

The exceptions to the Hierarchy Rule include justifiable homicide, aggravated assaults on law enforcement officers, motor vehicle theft, and arson. The FBI applies the following guidelines to convert those offenses.

  • "Justifiable homicide, by definition, occurs in conjunction with other offenses. Therefore, the crime being committed when the justifiable homicide took place must be reported as a separate offense. . . ." (UCR Handbook, 2004, page 17.)
  • When a law enforcement officer suffers an aggravated assault while responding to another crime, the officer's employing agency must report the officer's assault on the LEOKA Form 1-705. The agency should report the aggravated assault on the Return A only if it is the most serious offense within the incident. (UCR Handbook, 2004, page 110.)
  • "If a theft from a motor vehicle occurs in conjunction with a motor vehicle theft, reporting agencies must classify the incident as a motor vehicle theft." (UCR Handbook, 2004, page 33.)
  • In those situations where an arson occurs in conjunction with one or more additional offenses, the law enforcement agency should report the arson and apply the Hierarchy Rule to the remaining Part I offenses. (UCR Handbook, 2004, page 12.)

The FBI then selects the data elements pertinent to each Summary form and extracts particular data values to complete the details in as many columns and rows as possible.

The following pages detail the process by which the FBI converts NIBRS data to Summary data for each line of each respective Summary form and the LEOKA form. The information in this publication should prove helpful to agencies that want to replicate the FBI's procedures in order to produce the same data found in the Summary portion of the FBI's database.