V-Lab
State Street SPDR S&P 500 ETF Trust GAS-GARCH Student T Volatility Analysis
Volatility prediction for Monday, August 17th, 2026
1 Day
12.58%
decreased by 0.76%
1 Week
12.74%
decreased by 0.60%
1 Month
13.30%
decreased by 0.04%
Analysis last updated: Friday, August 14, 2026 at 10:45 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jan 29, 1993 to Aug 14, 2026Model Insight
Volatility shocks decay with a half-life of 63 trading days, meaning a shock loses half its impact after approximately 63 days. Returns follow a Student-t distribution with v = 6.79 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 | 1.3526 | 6.65*** |
α ARCH Response to squared shocks | 0.0922 | 41.19*** |
β GARCH Volatility persistence | 0.9890 | 555.61*** |
ν DF Student-t tail thickness | 6.7879 | 8.87*** |
Persistence:
0.989
Half-life:
63 days
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