Ishares S&P 500 EX S&P 1 ETF Zero Slope Spline-GARCH Volatility Analysis
Volatility prediction for Tuesday, October 20th, 2026
1 Day
12.03%
decreased by 0.05%
1 Week
12.06%
decreased by 0.02%
1 Month
12.15%
increased by 0.07%
Analysis last updated: Monday, October 19, 2026 at 09:58 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jul 9, 2025 to Oct 16, 2026Model Insight
This model fits a time-varying baseline (a spline), so volatility mean-reverts toward a slowly-shifting long-run level rather than a constant. Short-run deviations decay with a half-life of 29 trading days.
τ
Zero Slope Spline-GARCH Model
Tap to view equation
Time-varying baseline: volatility reverts to a slowly-shifting spline trend
| Param | Value | t-stat |
|---|---|---|
| ωconst | 1.0168 | 4.91*** |
| αARCH | 0.0109 | 0.59 |
| βGARCH | 0.9658 | 18.85*** |
Spline Coefficients
K=1
| γ1 | -0.0049 | -0.02 |
0.977
Persistence29d
Half-lifeτ
Zero Slope Spline-GARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 1.0168 | 4.91*** |
α ARCH Response to squared shocks | 0.0109 | 0.59 |
β GARCH Volatility persistence | 0.9658 | 18.85*** |
Spline Coefficients
K=1
| γ1 | -0.0049 | -0.02 |
Persistence:
0.977
Half-life:
29 days
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