There are three primary methods used to measure crime: the Uniform Crime Reports (UCR), the National Crime Victimization Survey (NCVS), and self-report surveys. The UCR is compiled by the FBI from data submitted by local, state, and federal law enforcement agencies. The UCR includes both violent and property crimes, but does not include crimes that were not reported to police. The NCVS is conducted by the Bureau of Justice Statistics and asks victims of crime about their experiences. The NCVS includes both violent and property crimes, and provides a more comprehensive picture of crime in the United States. Self-report surveys ask people whether they have committed any crimes in a given period of time. These surveys are generally considered to be the most accurate measure of crime, but they are also the most difficult to conduct.