US National AQI (top-10 metro mean)
Unweighted mean of daily AQI across the 10 most populous US metros.
— Current state —
— The series — full history —
Daily readings, every reading we have. Pick a window with the time-period buttons; flip to candles via the global toggle in the masthead (or press C). Toggle the SPY overlay to see how this series and the S&P 500 have moved together.
— What it has historically predicted —
On days when this signal fires (deviates 2+ standard deviations from its 30-day average, in either direction), SPY has historically averaged -4.2% over the next year, moving in the opposite direction 60% of the time.
— Beyond SPY — how this signal performs across markets —
Same fire days, different forward returns. Each row asks: when this signal fires, what does that asset do? The big number is the average return; underneath is how often the asset moved the same direction as the signal (50% would be a coin flip).
— Each fire in history — when the signal popped, what SPY did next —
Each bar is one historical fire — the indicator's value moved 2.5+ standard deviations from its rolling 180 trading-day mean (~9 months), or for monotonic “days since” indicators, crossed an 80th/90th/95th/99th percentile. Bar height = SPY's forward return at the selected horizon, signed by signal direction. Green above zero means the market moved with the signal; red below zero means it moved against.