V-Lab
State Street SPDR S&P 500 ETF Trust Zero Slope Spline-GARCH Volatility Analysis
Volatility prediction for Wednesday, September 9th, 2026
1 Day
11.64%
decreased by 0.05%
1 Week
12.09%
increased by 0.40%
1 Month
13.40%
increased by 1.71%
Analysis last updated: Tuesday, September 8, 2026 at 10:43 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jan 29, 1993 to Sep 4, 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 18 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 | 0.7067 | 4.69*** |
| αARCH | 0.1116 | 9.76*** |
| βGARCH | 0.8503 | 63.07*** |
Spline Coefficients
K=7
| γ1 | 0.0571 | 1.83* |
| γ2 | -0.1436 | -3.31*** |
| γ3 | 0.1621 | 6.52*** |
| γ4 | -0.1383 | -5.89*** |
| γ5 | 0.1047 | 3.60*** |
| γ6 | -0.0487 | -1.67* |
| γ7 | 0.0022 | 0.11 |
0.962
Persistence18d
Half-lifeτ
Zero Slope Spline-GARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.7067 | 4.69*** |
α ARCH Response to squared shocks | 0.1116 | 9.76*** |
β GARCH Volatility persistence | 0.8503 | 63.07*** |
Spline Coefficients
K=7
| γ1 | 0.0571 | 1.83* |
| γ2 | -0.1436 | -3.31*** |
| γ3 | 0.1621 | 6.52*** |
| γ4 | -0.1383 | -5.89*** |
| γ5 | 0.1047 | 3.60*** |
| γ6 | -0.0487 | -1.67* |
| γ7 | 0.0022 | 0.11 |
Persistence:
0.962
Half-life:
18 days
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