V-Lab
Vanguard S&P 500 Index ETF Zero Slope Spline-GARCH Volatility Analysis
Volatility prediction for Monday, August 10th, 2026
1 Day
19.81%
decreased by 1.68%
1 Week
19.33%
decreased by 2.16%
1 Month
17.90%
decreased by 3.59%
Analysis last updated: Saturday, August 8, 2026 at 09:18 AM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Nov 8, 2012 to Aug 7, 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 | 0.8586 | 10.66*** |
α ARCH Response to squared shocks | 0.1220 | 7.37*** |
β GARCH Volatility persistence | 0.8241 | 40.43*** |
Spline Coefficients
K=1
| γ1 | -0.0006 | -0.60 |
Persistence:
0.946
Half-life:
12 days
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