National crime in the US is reported through several methods: official police reporting of arrest and offense data collected by local and state law enforcement agencies and, since the late 1970s, federal agencies; self-report studies that survey offenders and victims directly; and victimization studies that survey victims about their experiences. The Uniform Crime Reporting program, managed by the FBI, collects and analyzes data on index/Part I crimes from law enforcement agencies nationwide, recording details on victims, offenders, and circumstances. Intimate partner violence poses challenges to accurately recording due to victims' fears of retaliation and difficulties collecting data on homeless populations.