When the FBI switched to a new data collection system, which relies on local police departments to report their numbers, about 40% of agencies didn’t switch over. The Marshall Project made an interactive to see who’s reporting data in your state:
Many criminologists fear the missing data means the nation would not get reliable crime data for years to come. If a local police department did not report crime data to the FBI, it would also mean scholars, policy makers and the public cannot compare what’s happening with crime in their community with other places.