This page documents how CrimeMaps.ca computes the CrimeMaps Severity Score (CMSS) — our severity-weighted crime rate modelled on Statistics Canada's Crime Severity Index.
Formula
CMSS = Σ (incidents_i × weight_i) / population × 100,000
Where incidents_i is the count of incidents in category i, weight_i is the Statistics Canada 2006-base severity weight for that category, and population is the 2021 Canadian Census population.
Weight table (version 1.0)
Derived verbatim from Statistics Canada Table 1 — Examples of weights for the Crime Severity Index (2006 base year). Categories we collapse (assault, sexual assault) use the published blend of level 1/2/3 weights.
| Category | Weight | Source |
|---|
| Homicide | 7,042 | UCR2 murder 1st & 2nd (verbatim) |
| Sexual assault | 323 | Blend: 0.80 × L1 (211) + 0.15 × L2 (678) + 0.05 × L3 (1,047) |
| Shooting | 988 | Discharging firearm with intent |
| Robbery | 583 | UCR2 robbery (verbatim) |
| Assault | 50 | Blend: 0.80 × L1 (23) + 0.15 × L2 (77) + 0.05 × L3 (405) |
| Break and enter | 187 | UCR2 B&E (verbatim) |
| Auto theft | 84 | UCR2 motor vehicle theft (verbatim) |
| Theft / Theft from vehicle / Bike theft | 37 | UCR2 theft under $5,000 |
| Fraud | 109 | UCR2 fraud (verbatim) |
| Mischief | 30 | UCR2 mischief (verbatim) |
| Other | 10 | Residual (low weight) |
How CMSS differs from Statistics Canada CSI
- Update cadence: Statistics Canada publishes CSI annually, with ~12 months of lag. CMSS updates as our scrapers pull new incidents (monthly / rolling 60-day).
- Data sources: CSI uses the UCR2 survey (every Canadian police service). CMSS uses municipal open-data portals — not every police service publishes openly, so coverage varies.
- Granularity: CSI publishes at Canada, province, and Census Metropolitan Area level. CMSS also publishes at neighbourhood level where we have polygons.
- Offence granularity: CSI uses ~100 UCR2 offence codes. CMSS uses 13 CrimeMaps categories (collapsed at ingest time).
Honest limitations
- Coverage bias. Cities that publish more offence types tend to rank higher on CMSS. Version 2.0 will normalise for coverage.
- Classification fidelity. Ambiguous raw offence strings map to "other" (weight 10). Every CMSS display shows the "other" share so readers can judge data quality.
- Population mismatch. Some police services cover an area larger than the CMA; dividing by CMA population can slightly inflate the rate.
- Weight base year. v1.0 uses 2006-base weights. Statistics Canada's current in-force weights (Index IV, 2021-2026) are ~17% higher. v2.0 will migrate.
Cities with limited data coverage
These cities are excluded from the CMSS rankings because their open-data feeds either report fewer than 1,000 incidents in the latest year or have a rate below 1,500 incidents per 100,000 residents — both strong signals that not every offence category is being published. Individual city pages still show absolute counts from the open-data feed as-is.
- Abbotsford, BC — 1,030 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Brampton, ON — 1,627 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Brantford, ON — 471 incidents (fewer than 1,000 incidents reported)
- Burnaby, BC — 177 incidents (fewer than 1,000 incidents reported)
- Caledon, ON — 2 incidents (fewer than 1,000 incidents reported)
- Calgary, AB — 2,009 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Cobourg, ON — 450 incidents (fewer than 1,000 incidents reported)
- Durham Region, ON — 1,339 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Guelph, ON — 512 incidents (fewer than 1,000 incidents reported)
- Halifax, NS — 918 incidents (fewer than 1,000 incidents reported)
- Halton Region, ON — 3,698 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Hamilton, ON — 396 incidents (fewer than 1,000 incidents reported)
- Langley, BC — 326 incidents (fewer than 1,000 incidents reported)
- London, ON — 3,265 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Mississauga, ON — 1,662 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Montreal, QC — 12,699 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Niagara Region, ON — 10 incidents (fewer than 1,000 incidents reported)
- Perth South, ON — 2 incidents (fewer than 1,000 incidents reported)
- Peterborough, ON — 925 incidents (fewer than 1,000 incidents reported)
- Prince George, BC — 653 incidents (fewer than 1,000 incidents reported)
- RCMP K-Division (AB), AB — 6,556 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Regina, SK — 469 incidents (fewer than 1,000 incidents reported)
- Richmond, BC — 259 incidents (fewer than 1,000 incidents reported)
- Saugeen Shores, ON — 122 incidents (fewer than 1,000 incidents reported)
- South Simcoe, ON — 164 incidents (fewer than 1,000 incidents reported)
- St. Marys, ON — 16 incidents (fewer than 1,000 incidents reported)
- Stratford, ON — 138 incidents (fewer than 1,000 incidents reported)
- Vancouver, BC — 1,683 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Waterloo Region, ON — 1,958 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
- Windsor, ON — 3,056 incidents (below 1,500 incidents per 100,000 residents (likely incomplete reporting))
Versioning
CMSS is versioned. Any weight change constitutes a new version. Every CMSS output in our aggregates.json includes the version field.
- v1.0 (2026-04-24) — initial release with Statistics Canada 2006-base weights, 13-category taxonomy, 2021 Census populations.
Source