"The presentation of large amounts of reported crime data in the same format, as is the case with the various country results reported on this web site, raises questions about the possibility of comparing reported crime levels in different countries.
In fact, experts generally regard cross-country comparisons of crime statistics as being characterized by methodological difficulties for the following three reasons:
Different definitions for specific crime types in different countries: The category in which any incident of victimization is recorded relies on the legal definition of crime in any country. Should that definition be different, and indeed this is often the case, comparisons will not in fact be made of exactly the same crime type. This is particularly the case in crimes that require some discretion from a police officer or relevant authority when they are identified. For example, the definitional difference between serious or common assault in different legal jurisdictions may be different, and this will be reflected in the total number of incidents recorded.
Different levels of reporting and traditions of policing: Different societies across the globe have been shown to have different levels of reporting of criminal incidents. This relates closely to levels of development in any society, most clearly reflected in accessibility to the police. Thus factors such as the number of police stations or telephones in any society impact upon reporting levels. The level of insurance coverage in any community is also a key indicator of the likelihood of citizens approaching the police as their claim for compensation may require such notification. In addition, in societies where the police are or have been mistrusted by the population, most specifically during periods of authoritarian rule, reporting levels are likely to be lower than in cases where the police are regarded as important members of the community.
Different social, economic and political contexts: Comparing crime data from societies that are fundamentally different may ignore key issues present in the society that impact upon levels of reporting. For example, different social norms in some societies may make it almost impossible for women to report cases of rape or sexual abuse, while in others, women are encouraged to come forward.
These factors, while alerting the reader to the potential pitfalls of comparisons, apply more to some crimes than others. In selected cases, most notably homicide, country to country comparisons are safer, although may still be subject to the drawbacks outlined above. In the case of some categories of violent crime - such as rape or assault - country to country comparisons may simply be unreliable and misleading.http://www.unodc.org/unodc/en/data-and-analysis/Compiling-and-comparing-International-Crime-Statistics.htmlMurder rate figs are safest and most reliable way to compare how violent different countries are.