OTTAWA — Statistics Canada rebuffed criticisms over crime data methodology levelled in a study released by an Ottawa think tank on Wednesday.

The study, published by the MacDonald-Laurier Institute For Public Policy, concluded that Statistics Canada's annual crime data report, Juristat, suffers from serious flaws because it doesn't take into account unreported crimes and uses flawed methodology for tracking violent crimes.

Scott Newark, a former Crown prosecutor and one-time adviser to Treasury Board President Stockwell Day who wrote the study, concluded that these flaws suggest Juristat needs a "sweeping set of reforms so the report can better fulfil its core, and commendable, purpose" of "giving Canadian policy-makers, opinion-makers, and citizens better information" on crime.

Chief among Newark's concerns is that StatsCan uses only police-reported crimes to determine how many crimes are reported each year, despite another annual StatsCan study released that examines the rate of crimes, typically property-related, that go unreported to police each year.

That study, the General Social Survey, found that "about three times as many crimes are committed as are reported to the police and that the rate of reporting is dropping," said Newark.

"That fewer crimes are being reported to the police does not lead to the conclusion that the volume of crime itself has dropped," said Newark, pointing to the 2009 Juristat's conclusion that crime rates continued their decade-long decline.

Newark said the Crime Severity Index (CSI), which StatsCan introduced in its 2008 report to measure the seriousness of offences by examining sentences handed out by judges, is "an inherently subjective standard, cited without supporting data and unreliable as a metric of serious crime."

If judges hand out shorter sentences, then the severity of the offences committed ought to be lower, the reasoning behind the index goes. And if sentences are getting shorter, than the severity of crime in Canada must be declining.

But Newark said that judges handing out shorter sentences is not necessarily a result of less violent crimes, but instead could result from institutional demands or the whims of judges themselves.

Newark said that switching to the CSI as a main measure of crime "reduced the amount of data readily available to readers to check the conclusions the report offered."

However, the director of StatsCan's Canadian Centre for Justice Statistics, Julie McAuley, said Newark's concerns over omitted data in Juristat are unfounded, as the yearly publication shouldn't be seen as the final word on crime statistics in Canada, but rather as complementary to the many studies, such as the General Social Survey, the agency releases.

"Taking one Juristat in isolation, while we try to cover as much as possible, the breadth of crime-related issues in that article, just given the length of the publication, it's not always possible for us to cover every single detail," said McAuley.

"We constantly do seek to update a number of our data over time," she said, suggesting that StatsCan has been using "better quality data" in recent years due to better reporting from police services. For example, criminal harassment and uttering threats were only included as violent crimes starting in 2008, making comparisons in the violent crime rate to years before then difficult.