JSE Securities South African Volatility Index Zero Slope Spline-GARCH Volatility Analysis
Volatility prediction for Friday, October 23rd, 2026
1 Day
85.21%
decreased by 2.95%
1 Week
90.26%
increased by 2.10%
1 Month
96.50%
increased by 8.34%
Analysis last updated: Friday, October 23, 2026 at 08:58 PM UTC
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News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Feb 1, 2007 to Oct 15, 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 3 trading days.
τ
Zero Slope Spline-GARCH Model
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Time-varying baseline: volatility reverts to a slowly-shifting spline trend
| Param | Value | t-stat |
|---|---|---|
| ωconst | 0.6684 | 4.64*** |
| αARCH | 0.1349 | 4.42*** |
| βGARCH | 0.6627 | 10.75*** |
Spline Coefficients
K=9
| γ1 | 0.0022 | 0.01 |
| γ2 | -0.1107 | -0.51 |
| γ3 | 0.3410 | 2.11** |
| γ4 | -0.5019 | -2.30** |
| γ5 | 0.4237 | 1.79* |
| γ6 | -0.0313 | -0.16 |
| γ7 | -0.4679 | -2.64*** |
| γ8 | 0.6878 | 4.06*** |
| γ9 | -0.4979 | -4.10*** |
0.798
Persistence3d
Half-lifeτ
Zero Slope Spline-GARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.6684 | 4.64*** |
α ARCH Response to squared shocks | 0.1349 | 4.42*** |
β GARCH Volatility persistence | 0.6627 | 10.75*** |
Spline Coefficients
K=9
| γ1 | 0.0022 | 0.01 |
| γ2 | -0.1107 | -0.51 |
| γ3 | 0.3410 | 2.11** |
| γ4 | -0.5019 | -2.30** |
| γ5 | 0.4237 | 1.79* |
| γ6 | -0.0313 | -0.16 |
| γ7 | -0.4679 | -2.64*** |
| γ8 | 0.6878 | 4.06*** |
| γ9 | -0.4979 | -4.10*** |
Persistence:
0.798
Half-life:
3 days
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