V-Lab
Vanguard S&P 500 Index ETF Zero Slope Spline-GARCH Volatility Analysis
Volatility prediction for Monday, August 24th, 2026
1 Day
12.56%
decreased by 0.67%
1 Week
12.77%
decreased by 0.46%
1 Month
13.32%
increased by 0.09%
Analysis last updated: Saturday, August 22, 2026 at 01:42 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Nov 8, 2012 to Aug 21, 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 12 trading days.
τ
Zero Slope Spline-GARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.8581 | 10.81*** |
α ARCH Response to squared shocks | 0.1224 | 7.36*** |
β GARCH Volatility persistence | 0.8222 | 39.90*** |
Spline Coefficients
K=1
| γ1 | -0.0006 | -0.57 |
Persistence:
0.945
Half-life:
12 days
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