Methodology
The score
livability=0.35*cost+0.30*climate+0.35*safety; cost=country PPP index x city-size premium (real population); safety=0.55*disaster_safety+0.45*crime_safety - urban-crime penalty (city size); disaster_safety=100-sum(hazard_weight*tier)/5*100 over 8 hazards (real earthquake/heat/cold + modelled flood/storm/wildfire/drought/tsunami); crime_safety=100-homicide*3
| Axis | Weight |
|---|---|
| Cost of living | 35% |
| Climate | 30% |
| Safety | 35% |
Hazard weights inside disaster safety
| Hazard | Weight |
|---|---|
| earthquake | 18% |
| flooding | 16% |
| storms (hurricane/cyclone) | 14% |
| wildfire | 12% |
| extreme heat | 12% |
| drought | 10% |
| tsunami | 10% |
| extreme cold / winter | 8% |
Measured vs modelled
Three hazards are measured directly: earthquake exposure counts real USGS events of magnitude 4.5+ within 300 km since 1980, and extreme heat and extreme cold come from WorldClim warmest- and coldest-month normals. The other five — flood, storm, wildfire, drought and tsunami — are modelled from real geophysical inputs (Koppen climate zone, elevation, cyclone-basin position, subduction-coast proximity, local seismicity). Modelled tiers are planning indicators, not engineering flood or seismic assessments.
Limitations
- Cost starts from a country-level World Bank price index adjusted by a modelled city-size premium. It is not a city-level price survey; official city data (US BEA RPP, Eurostat) is the next layer.
- Crime uses national homicide rate, which does not describe a specific neighbourhood.
- Climate normals describe a typical year, not a forecast and not a given season.
- Scores rank cities against each other. A high score is not a recommendation to move, and no score accounts for visas, tax, healthcare access or language.