V-Lab
PSI 20 Portuguese Stock Index GAS-GARCH Student T Volatility Analysis
Volatility prediction for Wednesday, September 16th, 2026
1 Day
12.17%
1 Week
12.33%
1 Month
12.93%
Analysis last updated: Tuesday, September 15, 2026 at 06:43 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Dec 30, 1992 to Sep 11, 2026Model Insight
With persistence 0.994, volatility shocks have a half-life of 124 trading days (~0.5 years), close to a unit root, so long-run forecasts are highly sensitive to this estimate. Returns follow a Student-t distribution with v = 6.73 degrees of freedom, capturing fatter tails than a normal distribution.
GAS-GARCH-T Model
Tap to view equation
| Param | Value | t-stat |
|---|---|---|
| ωconst | 1.9881 | 1.37 |
| αARCH | 0.0959 | 14.88*** |
| βGARCH | 0.9944 | 247.12*** |
| νDF | 6.7318 | 3.14*** |
0.994
Persistence124d
Half-lifeGAS-GARCH-T Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 1.9881 | 1.37 |
α ARCH Response to squared shocks | 0.0959 | 14.88*** |
β GARCH Volatility persistence | 0.9944 | 247.12*** |
ν DF Student-t tail thickness | 6.7318 | 3.14*** |
Persistence:
0.994
Half-life:
124 days
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