V-Lab
S&P GSCI Grains Spot Index GJR-GARCH Volatility Analysis
Volatility prediction for Monday, September 21st, 2026
1 Day
20.49%
decreased by 0.22%
1 Week
20.51%
decreased by 0.20%
1 Month
20.61%
decreased by 0.10%
Analysis last updated: Saturday, September 19, 2026 at 12:02 AM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jan 2, 1990 to Sep 18, 2026Model Insight
With persistence 0.990, volatility shocks have a half-life of 72 trading days (~0.3 years), close to a unit root, so long-run forecasts are highly sensitive to this estimate.
σ
GJR-GARCH Model
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High persistence: persistence 0.990, shock half-life ~72 days
| Param | Value | t-stat |
|---|---|---|
| ωconst | 0.0181 | 5.41*** |
| αARCH | 0.0656 | 6.10*** |
| βGARCH | 0.9340 | 157.05*** |
| γleverage | -0.0185 | -1.06 |
0.990
Persistence72d
Half-lifeσ
GJR-GARCH Model
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| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.0181 | 5.41*** |
α ARCH Response to squared shocks | 0.0656 | 6.10*** |
β GARCH Volatility persistence | 0.9340 | 157.05*** |
γ leverage Additional response to negative shocks | -0.0185 | -1.06 |
Persistence:
0.990
Half-life:
72 days
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