V-Lab
Vanguard S&P 500 ETF GAS-GARCH Student T Volatility Analysis
Volatility prediction for Wednesday, September 9th, 2026
1 Day
11.37%
increased by 0.06%
1 Week
11.69%
increased by 0.38%
1 Month
12.73%
increased by 1.42%
Analysis last updated: Tuesday, September 8, 2026 at 10:45 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Sep 9, 2010 to Sep 4, 2026Model Insight
Volatility shocks decay with a half-life of 27 trading days, meaning a shock loses half its impact after approximately 27 days. Returns follow a Student-t distribution with v = 6.70 degrees of freedom, capturing fatter tails than a normal distribution.
𝑓
GAS-GARCH-T Model
Tap to view equation
Shock decay: Shocks decay with a 27-day half-lifev = 6.70 · fat tails
| Param | Value | t-stat |
|---|---|---|
| ωconst | 1.1050 | 1.82* |
| αARCH | 0.1294 | 6.86*** |
| βGARCH | 0.9743 | 61.33*** |
| νDF | 6.6986 | 1.62 |
0.974
Persistence27d
Half-life𝑓
GAS-GARCH-T Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 1.1050 | 1.82* |
α ARCH Response to squared shocks | 0.1294 | 6.86*** |
β GARCH Volatility persistence | 0.9743 | 61.33*** |
ν DF Student-t tail thickness | 6.6986 | 1.62 |
Persistence:
0.974
Half-life:
27 days
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