V-Lab
S&P MidCap 400 Index GAS-GARCH Student T Volatility Analysis
Volatility prediction for Friday, September 25th, 2026
1 Day
12.10%
decreased by 0.36%
1 Week
12.31%
decreased by 0.15%
1 Month
13.06%
increased by 0.60%
Analysis last updated: Thursday, September 24, 2026 at 11:02 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jan 1, 1990 to Sep 18, 2026Model Insight
Volatility shocks decay with a half-life of 52 trading days, meaning a shock loses half its impact after approximately 52 days. Returns follow a Student-t distribution with v = 10.96 degrees of freedom, capturing fatter tails than a normal distribution.
𝑓
GAS-GARCH-T Model
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Shock decay: Shocks decay with a 52-day half-lifev = 10.96 · fat tails
| Param | Value | t-stat |
|---|---|---|
| ωconst | 1.3619 | 2.78*** |
| αARCH | 0.0884 | 9.26*** |
| βGARCH | 0.9866 | 177.71*** |
| νDF | 10.9565 | 1.12 |
0.987
Persistence52d
Half-life𝑓
GAS-GARCH-T Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 1.3619 | 2.78*** |
α ARCH Response to squared shocks | 0.0884 | 9.26*** |
β GARCH Volatility persistence | 0.9866 | 177.71*** |
ν DF Student-t tail thickness | 10.9565 | 1.12 |
Persistence:
0.987
Half-life:
52 days
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