V-Lab
Vanguard S&P 500 Index ETF GAS-GARCH Student T Volatility Analysis
Volatility prediction for Monday, August 24th, 2026
1 Day
11.83%
decreased by 0.72%
1 Week
12.05%
decreased by 0.50%
1 Month
12.65%
increased by 0.10%
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
Volatility shocks decay with a half-life of 14 trading days, meaning a shock loses half its impact after approximately 14 days. Returns follow a Student-t distribution with v = 8.77 degrees of freedom, capturing fatter tails than a normal distribution.
𝑓
GAS-GARCH-T Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.7717 | 16.52*** |
α ARCH Response to squared shocks | 0.1114 | 21.48*** |
β GARCH Volatility persistence | 0.9504 | 255.70*** |
ν DF Student-t tail thickness | 8.7704 | 3.80*** |
Persistence:
0.950
Half-life:
14 days
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