V-Lab
PSI 20 Portuguese Stock Index GARCH Volatility Analysis
Volatility prediction for Monday, September 28th, 2026
1 Day
12.76%
decreased by 0.75%
1 Week
13.05%
decreased by 0.46%
1 Month
14.09%
increased by 0.58%
Analysis last updated: Friday, September 25, 2026 at 05:03 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Dec 30, 1992 to Sep 25, 2026Model Insight
With persistence 0.993, volatility shocks have a half-life of 94 trading days (~0.4 years), close to a unit root, so long-run forecasts are highly sensitive to this estimate.
σ
GARCH Model
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High persistence: persistence 0.993, shock half-life ~94 days
| Param | Value | t-stat |
|---|---|---|
| ωconst | 0.0195 | 6.40*** |
| αARCH | 0.1354 | 12.44*** |
| βGARCH | 0.8572 | 88.34*** |
0.993
Persistence94d
Half-lifeσ
GARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.0195 | 6.40*** |
α ARCH Response to squared shocks | 0.1354 | 12.44*** |
β GARCH Volatility persistence | 0.8572 | 88.34*** |
Persistence:
0.993
Half-life:
94 days
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