The National Incident-Based Report System, NIBRS, implemented to improve the overall quality of crime data collected by law enforcement, captures details on each single crime incident - as well as on separate offenses within the same incident - including information on victims, known offenders, relationships between victims and offenders, arrestees, and property involved in the crimes.
Unlike data reported through UCR's traditional Summary System - an aggregate monthly tally of crimes - the NIBRS data goes much deeper because of its ability to provide circumstances and context for crimes. It includes all offenses within a single incident and additional aspects about each event like location, time of day, and whether the incident was cleared. Ultimately, NIBRS will improve the detail and overall quality of crime data, which will help law enforcement and communities around the country use resources more strategically and effectively.
However, only about a third of all US law enforcement agencies currently participate in NIBRS. Transitioning to the new system can be somewhat costly, and because of the greater level of reporting specificity in NIBRS - it can initially appear that an agency has higher levels of crime after switching to NIBRS. But because the NIBRS can provide more useful statistics that will promote constructive discussion, measured planning, and informed policing, FBI Director James Comey has made implementation of the NIBRS a top priority.
The UCR program is actively working to increase NIBRS participation by partnering with the Bureau of Justice Statistics on the National Crime Statistics Exchange, working with advocacy groups to emphasize the importance of NIBRS data for the public and the law enforcement community, and transitioning the UCR program to a NIBRS only data collection by 2021.
The vision for the NIBRS is for it to become the law enforcement community's standard for quantifying crime, further supporting the mission for the FBI UCR Program to generate reliable information for us in law enforcement administration, operation, and management.
-quoted from FBI: UCR NIBRS Overview