Statistics Canada Report on How Often Police Solve Crimes

Statistics Canada has published an article in its Juristat publication on Police-reported clearance rates in Canada, 2010.

The article shows that police are solving more crimes than in the past.

Among the highlights:

• In 2010, three-quarters of homicides were solved by police. Clearance rates for homicide have gradually declined from around 95% in the early 1960s when data were first collected.
• In 2010, almost three-quarters of violent crimes were solved by police compared with about one-quarter of property crimes.
• Police solved just over 8 in 10 aggravated assault and aggravated sexual assault incidents in 2010, among the highest clearance rates for violent offences. 
• About 4 in 10 robberies were solved by police, the lowest of any violent offence.
• Clearance rates for property crimes were somewhat lower. For example, police cleared about 1 in 6 break-ins and 1 in 7 motor vehicle thefts in 2010.

Overall, the so-called "weighted clearance rate" rose for the seventh consecutive year to 39.4% in 2010, up from 33.5% in 2003:

"The clearance rate represents the proportion of criminal incidents solved by the police. Police can clear an incident by charge or by means other than the laying of a charge. For an incident to be cleared by charge, at least one accused must have been identified and either a charge has been laid, or recommended to be laid, against this individual in connection with the incident. For an incident to be cleared otherwise, an accused must be identified and there must be sufficient evidence to lay a charge in connection with the incident, but the accused is processed by other means for one of many reasons (...)"

"Total clearance rates share the same limitation as total crime rates in that overall totals are dominated by high-volume, less-serious offences such as minor thefts, mischief and minor assaults. Many of these less-serious offences which drive the overall clearance rate are often difficult to solve. For example, by the time an incident of graffiti/mischief to property is reported to police, the accused may no longer be present at the crime scene, nor will there likely be any witnesses. In the calculation of the overall clearance rate, all offences are counted equally: the clearance of one mischief incident by police counts the same as the solving of one homicide incident."

"To address this limitation, a 'weighted' clearance rate was developed, similar to the concept used in the Crime Severity Index. The weighted clearance rate assigns values to crimes according to their seriousness, with more serious crimes being given a higher statistical 'weight'. For example, the clearing of a homicide, robbery or break-in would represent a greater contribution to the overall weighted clearance rate value than the clearing of a minor theft, mischief or disturbing the peace. The severity of an offence is determined using average sentences handed down by Canadian criminal courts. The more serious the average sentence for an offence, the higher the weight and, in turn, the greater impact on the overall clearance rate."