V-Lab
Vanguard S&P 500 Index ETF Spline-GARCH Volatility Analysis
Volatility prediction for Friday, August 7th, 2026
1 Day
21.69%
decreased by 1.81%
1 Week
21.15%
decreased by 2.35%
1 Month
19.52%
decreased by 3.98%
Analysis last updated: Friday, August 7, 2026 at 09:09 AM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Nov 8, 2012 to Jul 31, 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 13 trading days.
τ
Spline-GARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.9077 | 9.63*** |
α ARCH Response to squared shocks | 0.1202 | 7.37*** |
β GARCH Volatility persistence | 0.8259 | 41.39*** |
Spline Coefficients
K=1
| γ1 | 0.0030 | 0.72 |
Persistence:
0.946
Half-life:
13 days
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