The Nation's Two Crime Measures
The U.S. Department of Justice administers two statistical programs to measure the magnitude, nature, and impact of crime in the nation: the Uniform Crime Reporting (UCR) Program and the National Crime Victimization Survey (NCVS). Each of these programs produces valuable information about aspects of the nation’s crime problem. Because the UCR and NCVS programs have different purposes, use different methods, and focus on somewhat different aspects of crime, the complementary information they produce together provides a more comprehensive understanding of the nation’s crime problem than either could produce alone.
Uniform Crime Reports
The International Association of Chiefs of Police (IACP) began publishing information for the UCR Program in 1929, two years after the IACP had established a committee to research the uniform reporting of crime statistics. Since September 1930, the FBI has administered the program, which currently collects information on murder and nonnegligent manslaughter, rape, robbery, aggravated assault, burglary, larceny-theft, motor vehicle theft, arson, cargo theft, and human trafficking through the Summary Reporting System (SRS). Law enforcement agencies report arrest data for 20 additional crime categories.
The UCR Program compiles data from monthly law enforcement reports or individual crime incident records transmitted directly to the FBI or to centralized agencies that then report to the FBI. The program thoroughly examines each report it receives for reasonableness, accuracy, and deviations that may indicate errors. Large variations in crime levels may indicate modified records procedures, incomplete reporting, or changes in a jurisdiction’s boundaries. To identify any unusual fluctuations in an agency’s crime counts, the program compares monthly reports to previous submissions from the agency and with those for similar agencies.
The UCR Program presents crime counts for the nation as a whole, as well as for regions, states, counties, cities, towns, tribal law enforcement, and colleges and universities. This permits analysis among neighboring jurisdictions and among those with similar populations and other common characteristics.
The FBI annually publishes its findings in a detailed annual report, Crime in the United States, issued in the fall. In addition to crime counts and trends, this report includes data on crimes cleared, persons arrested (age, sex, race, and ethnicity), law enforcement personnel, and the characteristics of homicides (including age, sex, and race of victims and offenders; victim-offender relationships; weapons used; and circumstances surrounding the homicides). The UCR Program also generates other periodic reports.
Many local and state law enforcement agencies participating in the UCR Program submit their UCR data via the more comprehensive National Incident-Based Reporting System (NIBRS). The NIBRS provides agencies the opportunity to submit additional details about each criminal incident in 23 broad categories of offenses. The NIBRS furnishes incident and offense data, as well as characteristics of all victims, offenders, and arrestees (age, sex, race, and ethnicity; and victim-offender relationships). The collection includes weapons data, location types, drug information, property descriptions, the type of criminal activity or gang involvement; and it offers the ability for greater analysis.
National Crime Victimization Survey
The NCVS, administered by the Bureau of Justice Statistics (BJS), provides a detailed picture of crime incidents, victims, and trends. The program began in 1973 as the National Crime Survey (NCS). In 1992, the NCS was renamed the NCVS to reflect a substantial redesign effort that focused primarily on methodological changes to the survey. The redesign also improved the initial questions used to screen for victimization incidents, updated the survey methods to take advantage of new technologies, and broadened the scope of crimes measured. The current NCVS collects detailed information on the frequency and nature of the crimes of rape and other sexual assault, robbery, aggravated and simple assault, personal larceny, household burglary, motor
vehicle theft, and other theft.
Each year, the BJS interviews a nationally representative sample of approximately 160,000 persons age 12 or older living in households across the nation. Households remain in the sample for 3 years. New households rotate into the sample on an ongoing basis.
The NCVS collects information on crimes experienced by individuals and households during the six months preceding the interview, whether or not those crimes were reported to law enforcement. A unique feature of the NCVS is that it collects both reported and unreported crimes and reasons why the crime was or was not reported.
The survey also captures specific details about each crime incident. The NCVS collects information about victims (such as age, sex, race, ethnicity, marital status, income, and educational level), offenders (such as sex, race, approximate age, and victim-offender relationship), and the crimes (including time and place of occurrence, use of weapons, nature of injury, and economic consequences). In addition, the NCVS asks questions about the experiences of victims with the criminal justice system, self-protective measures used by victims, and possible substance abuse by offenders. The NCVS periodically includes additional questions on particular topics. Recent supplements have covered issues concerning school crime, identity theft, contacts between police and citizens, and stalking.
BJS publishes NCVS data in Criminal Victimization, an annual report that covers the broad range of detailed information collected by the NCVS, and the NCVS Victimization Analysis Tool, an online database through which users can examine victimization rates, counts, and percentages by a range of victim and crime characteristics. The BJS also publishes detailed reports on topics such as intimate partner violence, workplace violence, hate crime, and crime against persons with disabilities. The National Archive of Criminal Justice Data at the University of Michigan archives the NCVS data files to enable researchers to perform independent analyses.
Comparing UCR and the NCVS
Because the BJS designed the NCVS in part to complement the UCR Program, the two programs share many similarities. As much as their different collection methods permit, the two measure the same subset of serious crimes, defined alike. Both programs cover rape, robbery, aggravated assault, burglary, theft, and motor vehicle theft. Rape, robbery, theft, and motor vehicle theft are defined virtually identically by both the UCR Program and the NCVS. (Prior to 2013, the UCR Program measured a more limited definition of forcible rape against women only, while the NCVS measured a broader definition of rape against both sexes. Now the NCVS and the UCR Program define rape analogously.)
Despite covering a set of similar crimes, the two programs differ significantly. First, the two programs serve different purposes. The UCR Program’s primary objective is to provide a reliable set of criminal justice statistics for law enforcement administration, operation, and management. The BJS established the NCVS to provide previously unavailable information about crime (including crime not reported to police), victims, and offenders.
Second, the two programs measure an overlapping but nonidentical set of crimes. The NCVS includes, but the UCR Program’s SRS excludes, sexual assault (completed, attempted, and threatened), attempted robberies, verbal threats of rape, simple assault, and crimes not reported to law enforcement. The UCR includes, but the NCVS excludes, homicide, arson, commercial crimes, and crimes against children under age 12. The UCR Program’s SRS also captures crimes reported to law enforcement but collects only arrest data for simple assault and sex offenses other than rape.
Third, because of methodology, the NCVS and UCR definitions of some crimes differ. For example, the UCR SRS defines burglary as the unlawful entry or attempted entry of a structure to commit a felony or theft. The NCVS defines burglary as the entry or attempted entry of a residence by a person who had no right to be there.
Fourth, for property crimes (burglary, theft, and motor vehicle theft), the two programs calculate crime rates using different bases. The UCR rates for these crimes are per capita (number of crimes per 100,000 persons), whereas the NCVS rates for these crimes are per household (number of crimes per 1,000 households).
Because the number of households may not grow at the same rate each year as the total population, trend data for rates of property crimes measured by the two programs may not be comparable. In addition, some differences in the data from the two programs may result from sampling variation in the NCVS and from estimating for nonresponse in the UCR.
The BJS derives the NCVS estimates from interviewing a sample. The estimates are subject to a margin of error. This error is known and is reflected in the standard error of the estimate. The UCR Program bases its data on the actual counts of offenses reported by law enforcement agencies. In some circumstances, the UCR Program estimates its data for nonparticipating agencies or those reporting partial data. Apparent discrepancies between statistics from the two programs can usually be accounted for by differences in definitions or procedures or resolved by comparing NCVS sampling variations (confidence intervals) of those crimes said to have been reported to police with UCR statistics.
Each program has unique strengths. The UCR provides a measure of the number of crimes reported to law enforcement agencies throughout the country. The UCR SRS’s Supplementary Homicide Reports provide reliable, timely data on the extent and nature of homicides in the nation. In addition to providing annual point and change estimates on criminal victimization, the NCVS is the primary source of information on the characteristics of criminal victimization incidents and on the number and types of crimes not reported to law enforcement authorities.
By understanding the strengths and limitations of each program, it is possible to use the UCR and the NCVS to achieve a greater understanding of crime trends and the nature of crime in the United States. For example, changes in police procedures, shifting attitudes towards crime and police, and other societal changes can affect the extent to which people report and law enforcement agencies record crime. NCVS and UCR data can be used in complementary ways to explore why trends in reported and police-recorded crime may differ.