Measuring crime is an important and complex task. The four main sources of crime statistics are: the Uniform Crime Reports (UCR), the National Incident-Based Reporting System (NIBRS), the National Crime Victimization Survey (NCVS), and self-report studies. All methods are flawed and do not measure the total amount of crime. The unknown amount is called the dark figure of crime, and includes offenses that are not reported and offenses that are reported but not recorded. Victims may choose not to report an offense to the police for many reasons. However, the major sources of crime data tend to show some agreement in pattern if not in volume.
The UCR has data on crimes reported to the police and is run by the FBI. It measures four property and four violent crimes and includes both the number of crimes and the crime rate. The UCR has several problems, including the hierarchy rule and the absence of information on crimes not reported to the police. NIBRS was designed as an improvement upon the UCR and includes information on more types of offenses reported to the police. However, although it does not use the hierarchy rule, it is still underdeveloped. The NCVS is the main source of victimization data in the United States and includes information from individuals ages 12 and older from a sample of households. Unlike the UCR and NCVS, it gathers information about offenses even if they were not reported to the police and thus provides information about the dark figure of crime. However, it also has problems, many of which are related to under-reporting and over-reporting of victimization. The three sources do not produce matching statistics but have shown patterns of convergence and divergence. Current economic issues are threatening the future of these programs.
Self-report studies ask individuals about any illegal activities they have committed within a given period of time. Many are carried out with youths, young adults, or juvenile delinquents. They also have problems, including a reliance on samples and concerns about both validity and reliability. Some of the main self-report studies today include the National Youth Survey Family Study, Monitoring the Future, and the National Survey on Drug Use and Health.
These four sources of data provide a complementary picture of crime and together help to provide a clearer and more accurate view of the nature and extent of crime in the United States.