Crime rates

Several methods for measuring crime exist. Public surveys are sometimes conducted to estimate the amount of crime not reported to police. Such surveys are usually more reliable for assessing trends. However, they also have their limitations and generally don't procure statistics useful for local crime prevention, often ignore offenses against children and do not count offenders brought before the criminal justice system.

Law enforcement agencies in some countries offer compilations of statistics for various types of crime.

Two major methods for collecting crime data are law enforcement reports, which only reflect crimes that are reported, recorded, and not subsequently canceled; and victim study (victimization statistical surveys), which rely on individual memory and honesty. For less frequent crimes such as intentional homicide and armed robbery, reported incidences are generally more reliable, but suffer from under-recording; for example, no criming in the United Kingdom sees over one third of reported violent crimes being not recorded by the police. Because laws and practices vary between jurisdictions, comparing crime statistics between and even within countries can be difficult: typically only violent deaths (homicide or manslaughter) can reliably be compared, due to consistent and high reporting and relative clear definition.

The U.S. has two major data collection programs, the Uniform Crime Reports from the FBI and the National Crime Victimization Survey from the Bureau of Justice Statistics. However, the U.S. has no comprehensive infrastructure to monitor crime trends and report the information to related parties such as law enforcement.

Research using a series of victim surveys in 18 countries of the European Union, funded by the European Commission, has reported (2005) that the level of crime in Europe has fallen back to the levels of 1990, and notes that levels of common crime have shown declining trends in the U.S., Canada, Australia and other industrialized countries as well. The European researchers say a general consensus identifies demographic change as the leading cause for this international trend. Although homicide and robbery rates rose in the U.S. in the 1980s, by the end of the century they had declined by 40%.

However, the European research suggests that "increased use of crime prevention measures may indeed be the common factor behind the near universal decrease in overall levels of crime in the Western world", since decreases have been most pronounced in property crime and less so, if at all, in contact crimes.

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