The two main governmental systems for measuring crime are:

• Uniform Crime Reports (UCR): UCR data are compiled from monthly law enforcement reports or individual crime incident records transmitted directly to the FBI or to centralized state agencies that then report to the FBI
• National Criminal Victimization Survey (NCVS): The NCVS collects information by survey on crimes suffered by individuals and households, whether or not those crimes were reported to law enforcement.

When looking for statistics on any criminal justice subject it is important to consult both UCR and NCVS statistics. The shortcoming of UCR data is that it relies on official reports, and we know that many crimes are never actually reported to police. The shortcoming of NCVS data is that it relies on surveys of citizens and there is no assurance that people's survey responses are accurate. The best overall picture comes from looking at both kinds of data.

Next: Major Government Agencies That Collect Criminal Justice Statistics