V-Lab
PSI 20 Portuguese Stock Index AGARCH Volatility Analysis
Volatility prediction for Monday, August 31st, 2026
1 Day
10.10%
decreased by 0.08%
1 Week
10.58%
increased by 0.40%
1 Month
12.18%
increased by 2.00%
Analysis last updated: Friday, August 28, 2026 at 05:04 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Dec 30, 1992 to Aug 28, 2026Model Insight
The news-impact curve is shifted (γ = 0.20) so that negative returns raise next-day volatility more than positive returns of the same size. The gap is largest for small shocks and narrows for larger ones.
σ
AGARCH Model
Tap to view equation
| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.0210 | 20.89*** |
α ARCH Response to squared shocks | 0.1295 | 50.71*** |
β GARCH Volatility persistence | 0.8559 | 351.94*** |
γ leverage Additional response to negative shocks | 0.1974 | 16.49*** |
Persistence:
0.985
Half-life:
47 days
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