PSI 20 Portuguese Stock Index Asy. Power MEM Volatility Analysis
Volatility prediction for Tuesday, October 20th, 2026
1 Day
12.95%
1 Week
12.56%
1 Month
11.44%
Analysis last updated: Monday, October 19, 2026 at 05:13 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jul 18, 1997 to Oct 16, 2026Model Insight
This asset exhibits a modest leverage effect: negative returns increase next-day volatility 35% more than equivalent positive returns. The volatility power δ = 1.11 sits below 2, so large shocks influence volatility less than quadratically, a more outlier-robust response than standard GARCH.
APMEM Model
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| Param | Value | t-stat |
|---|---|---|
| ωconst | 0.0277 | 7.88*** |
| αARCH | 0.2370 | 19.81*** |
| βGARCH | 0.7565 | 64.58*** |
| γleverage | 0.1354 | 6.89*** |
| δpower | 1.1096 | 6.55*** |
0.948
Persistence13d
Half-lifeAPMEM Model
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| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.0277 | 7.88*** |
α ARCH Response to squared shocks | 0.2370 | 19.81*** |
β GARCH Volatility persistence | 0.7565 | 64.58*** |
γ leverage Additional response to negative shocks | 0.1354 | 6.89*** |
δ power Transformation power | 1.1096 | 6.55*** |
Persistence:
0.948
Half-life:
13 days
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