In England and Wales, official crime statistics have been produced each year for about 150 years. They are a major source for planning policy and resources for the criminal justice system. In addition, they influence ideas about the extent and nature of crime. Although they are often taken as showing the actual amount of crime, they only represent the total of serious offenses known by the police. Some crimes are undiscovered. Others are thought to be accidents. Stolen articles may be assumed to be lost, for example. Victims may not report crimes for a variety of reasons. The police exercise discretion over whether to record a crime, usually basing their decision on the amount of evidence provided by the witness. The British Crime Survey, first conducted in 1982 and repeated in 1984, is a broad-based method of improving knowledge about crime. It focuses on the victims' perspectives and experiences and shows that far more crime exists than is recorded. Nevertheless, public debates attach great significance to official crime figures.