Why Thunder Bay's Crime Severity Index Needs Context
The CSI is a useful national yardstick - and one of the most misread statistics in Canadian journalism.
Each summer, Statistics Canada releases the Crime Severity Index (CSI), and each summer Thunder Bay's high ranking generates headlines. The CSI is a genuinely useful tool, but it is widely misunderstood.
The index weights offences by seriousness, so a small number of grave crimes can lift a smaller city's score dramatically. In a community of Thunder Bay's size, a handful of cases - tragic as they are - can swing the ranking far more than they would in a metro area of millions.
What the index does well
It lets us compare year over year and against other cities on a consistent basis. What it doesn't do is tell an individual resident how safe their street is on a Tuesday night. For that, local trends, repeat-location data, and the share of violence between people who know each other are far more informative.
Our standing editorial position: report the CSI, but never without the denominator and the trend.
