Uniform Crime Reports
The UCR is the FBI’s widely used system for recording crimes and making policy decisions. It has tracked data on seven crimes since 1930: murder, robbery, rape, aggravated assault, burglary, theft and vehicle theft. In 1979, the UCR started reporting on arson. Nearly 17,000 law enforcement agencies report UCR data to the FBI but those data have several limitations that make them unsuitable for analyzing local crime.
National Incident-Based Reporting System
Crime data from NIBRS (as of 2004) come from 5,271 law enforcement agencies that represent about 20 percent of the total U.S. population. NIBRS is the result of the FBI's efforts in the 1980s to revise the UCR.
|Uniform Crime Reports||National Incident-Based Reporting System|
|Tracks eight crimes.||Tracks 46 crimes.|
|Does report arrests in specific incidents.||Contains information about arrests in each incident.|
|Gives a tally of the incidents. Does not contain information on each reported incident.||Contains information on each incident reported to police, including:
|Does not provide information about simple assault, which is the most commonly reported domestic violence offense.||Provides information about cases involving simple assault.|
|Reports only the most serious crime committed in a single incident (e.g., if a murderer has raped his victim, only murder is reported.)||Requires officers to report multiple offenses, victims and individuals committing offenses. This allows researchers to compare and analyze multiple incidents.|
Impact of NIBRS on Law Enforcement
NIBRS significantly expands officers’ ability to record data about a specific incident, which gives leaders a much fuller understanding of crime. As a result, a mayor’s policy advisor or a police executive can look at NIBRS data alone or combine them with other citywide data, analyze them, and gain a more descriptive view of criminal activity in the
community. NIBRS data help law enforcement gather better evidence to develop effective solutions and practices.
Impact of NIBRS on Research
Researchers find NIBRS data useful and have successfully used NIBRS data to:
- Assess dual arrest data. Researchers used NIBRS data to examine the factors that influence police decisions to make arrests in domestic violence incidents and the prevalence of dual arrest across the nation.  They found that dual arrest occurs more in same-sex than in heterosexual relationships and in states that have mandatory arrest policies but no primary aggressor provisions.  The researchers suggest that if a state wants to minimize dual arrests, agencies may wish to institute primary aggressor provisions, change mandatory arrest policies to preferred arrest policies, and educate officers about relationship dynamics in same-sex relationships. (Read the full report Explaining the Prevalence, Context, and Consequences of Dual Arrest in Intimate Partner Violence Cases (pdf, 207 pages).
- Examine drug distribution. A 1999 study used NIBRS data to examine rates of drug sales and distribution in three Virginia communities. Police identified drug sales that crossed jurisdictional boundaries and were able to develop policies and protocols to capture persons who commit drug offenses. 
[note 1] Dual arrest occurs when an officer arrests multiple parties in an incident as mutual combatants.
[note 2] A primary aggressor provision instructs officers to arrest only the main suspect in an incident.
[note 3] For more information, see Faggiani, D., and C. McLaughlin, “Using National Incident-Based Reporting System Data for Strategic Crime Analysis,” Journal of Quantitative Criminology 15(2) (1999): 181–191.