S&P 500 Equal Weight Index (EWI) GARCH Volatility Analysis
Volatility prediction for Friday, October 9th, 2026
1 Day
10.77%
increased by 0.01%
1 Week
11.01%
increased by 0.25%
1 Month
11.85%
increased by 1.09%
Analysis last updated: Friday, October 9, 2026 at 04:03 AM UTC
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News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jan 1, 1990 to Oct 2, 2026Model Insight
Volatility shocks decay with a half-life of 50 trading days, meaning a shock loses half its impact after approximately 50 days.
σ
GARCH Model
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Shock decay: Shocks decay with a 50-day half-life
| Param | Value | t-stat |
|---|---|---|
| ωconst | 0.0169 | 5.52*** |
| αARCH | 0.0986 | 9.98*** |
| βGARCH | 0.8876 | 87.79*** |
0.986
Persistence50d
Half-lifeσ
GARCH Model
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| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.0169 | 5.52*** |
α ARCH Response to squared shocks | 0.0986 | 9.98*** |
β GARCH Volatility persistence | 0.8876 | 87.79*** |
Persistence:
0.986
Half-life:
50 days
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