V-Lab
Ishares S&P 500 EX S&P 1 ETF Zero Slope Spline-GARCH Volatility Analysis
Volatility prediction for Tuesday, September 29th, 2026
1 Day
12.42%
decreased by 0.01%
1 Week
12.44%
increased by 0.01%
1 Month
12.52%
increased by 0.09%
Analysis last updated: Monday, September 28, 2026 at 09:57 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jul 9, 2025 to Sep 25, 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 | 0.9939 | 4.37*** |
| αARCH | 0.0074 | 0.40 |
| βGARCH | 0.9687 | 17.32*** |
Spline Coefficients
K=1
| γ1 | -0.0457 | -0.16 |
0.976
Persistence29d
Half-lifeτ
Zero Slope Spline-GARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.9939 | 4.37*** |
α ARCH Response to squared shocks | 0.0074 | 0.40 |
β GARCH Volatility persistence | 0.9687 | 17.32*** |
Spline Coefficients
K=1
| γ1 | -0.0457 | -0.16 |
Persistence:
0.976
Half-life:
29 days
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