V-Lab
State Street SPDR S&P 500 ETF Trust Zero Slope Spline-GARCH Volatility Analysis
Volatility prediction for Monday, August 17th, 2026
1 Day
12.89%
decreased by 0.56%
1 Week
13.23%
decreased by 0.22%
1 Month
14.25%
increased by 0.80%
Analysis last updated: Friday, August 14, 2026 at 10:44 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jan 29, 1993 to Aug 14, 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
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.7051 | 4.64*** |
α ARCH Response to squared shocks | 0.1115 | 9.77*** |
β GARCH Volatility persistence | 0.8508 | 63.48*** |
Spline Coefficients
K=7
| γ1 | 0.0570 | 1.81* |
| γ2 | -0.1438 | -3.28*** |
| γ3 | 0.1625 | 6.50*** |
| γ4 | -0.1380 | -5.82*** |
| γ5 | 0.1032 | 3.52*** |
| γ6 | -0.0460 | -1.57 |
| γ7 | -0.0002 | -0.01 |
Persistence:
0.962
Half-life:
18 days
Other State Street SPDR S&P 500 ETF Trust Analyses
Other Zero Slope Spline-GARCH Analyses on ETFs