V-Lab
PSI 20 Portuguese Stock Index GJR-GARCH Volatility Analysis
Volatility prediction for Tuesday, August 25th, 2026
1 Day
10.38%
decreased by 0.33%
1 Week
10.82%
increased by 0.11%
1 Month
12.26%
increased by 1.55%
Analysis last updated: Monday, August 24, 2026 at 05:12 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Dec 30, 1992 to Aug 21, 2026Model Insight
This asset exhibits a strong leverage effect: negative returns increase next-day volatility 101% more than equivalent positive returns.
σ
GJR-GARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.0244 | 27.09*** |
α ARCH Response to squared shocks | 0.0859 | 27.35*** |
β GARCH Volatility persistence | 0.8569 | 378.32*** |
γ leverage Additional response to negative shocks | 0.0865 | 11.20*** |
Persistence:
0.986
Half-life:
49 days
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