Crime statistics attempt to provide statistical measures of the crime in societies. Given that crime is illegal, measurements of it are likely to be inaccurate.

Several methods for measuring crime exist, including household surveys, hospital or insurance records, and compilations by police and similar law enforcement agencies. Typically official crime statistics are the latter, but some offences are likely to go unreported to the police. Public surveys are sometimes conducted to estimate the amount of crime not reported to police. Such surveys are usually more reliable for assessing trends. Public surveys rarely encompass all crime, rarely procure statistics useful for local crime prevention, often ignore offences against children, and do not count offenders brought before the criminal justice system.

Crime statistics are gathered and reported by many countries and are of interest to several international organizations, including Interpol and the United Nations. Law enforcement agencies in some countries, such as the FBI in the United States and the Home Office in England & Wales, publish crime indices, which are compilations of statistics for various types of crime.

Data collection and organization

Statistics are usually collected on:

• Offences - Breaches of the law
• Offenders - Those who commit offences
• Victims - Those who are offended against

Two major methods for collecting crime data are law enforcement reports, which only reflect reported crimes and victimization statistical surveys, which rely on individual honesty. For less frequent crimes such as intentional homicide and armed robbery, reported incidences are generally more reliable. Because laws vary between jurisdictions, comparing crime statistics between and even within countries can be difficult.

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.Committee on Understanding Crime Trends, U.S. National Research Council. (2008). Understanding Crime Trends: Workshop Report. National Academies Press. Free full-text.

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%.