V-Lab
JSE Securities South African Volatility Index Zero Slope Spline-GARCH Volatility Analysis
Volatility prediction for Friday, September 11th, 2026
1 Day
84.00%
decreased by 0.70%
1 Week
91.34%
increased by 6.64%
1 Month
100.28%
increased by 15.58%
Analysis last updated: Saturday, September 12, 2026 at 12:48 AM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Feb 1, 2007 to Sep 10, 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
Tap to view equation
Time-varying baseline: volatility reverts to a slowly-shifting spline trend
| Param | Value | t-stat |
|---|---|---|
| ωconst | 0.6759 | 4.67*** |
| αARCH | 0.1350 | 4.45*** |
| βGARCH | 0.6645 | 10.88*** |
Spline Coefficients
K=9
| γ1 | 0.0094 | 0.06 |
| γ2 | -0.1222 | -0.55 |
| γ3 | 0.3495 | 2.12** |
| γ4 | -0.5057 | -2.28** |
| γ5 | 0.4145 | 1.73* |
| γ6 | -0.0068 | -0.03 |
| γ7 | -0.4969 | -2.76*** |
| γ8 | 0.7083 | 4.10*** |
| γ9 | -0.5085 | -4.04*** |
0.799
Persistence3d
Half-lifeτ
Zero Slope Spline-GARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.6759 | 4.67*** |
α ARCH Response to squared shocks | 0.1350 | 4.45*** |
β GARCH Volatility persistence | 0.6645 | 10.88*** |
Spline Coefficients
K=9
| γ1 | 0.0094 | 0.06 |
| γ2 | -0.1222 | -0.55 |
| γ3 | 0.3495 | 2.12** |
| γ4 | -0.5057 | -2.28** |
| γ5 | 0.4145 | 1.73* |
| γ6 | -0.0068 | -0.03 |
| γ7 | -0.4969 | -2.76*** |
| γ8 | 0.7083 | 4.10*** |
| γ9 | -0.5085 | -4.04*** |
Persistence:
0.799
Half-life:
3 days
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