Our Scoring Methodology

We don't trust simple averages. Our algorithm is built to penalize hidden risks that other indices miss.

1 Base Air Quality (40%)

We start with the annual average PM2.5 concentration. We benchmark against World Health Organization (WHO) targets, not just EPA limits.

< 5 µg/m³: Perfect Score (100)
> 12 µg/m³: Failing Score (0)

2 The "Extreme Day" Penalty (30%)

A city can have a good average but still be dangerous during wildfire season. We aggressively penalize days with AQI > 100.

🚨 Automatic Fail Rule: Any city with more than 30 unhealthy days per year cannot score above 59/100, regardless of other metrics.

3 5-Year Trend (20%)

Retirement is a long-term commitment. We analyze 5 years of historical data to reward cities that are getting cleaner and punish those that are stagnant or worsening.

4 Stability (10%)

Consistency matters for health. We calculate the volatility between the best and worst months. Stable climates score higher.