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V-Lab

PSI 20 Portuguese Stock Index GAS-GARCH Student T Volatility Analysis

Volatility prediction for Thursday, October 1st, 2026

1 Day

11.16%

decreased by 0.76%

1 Week

11.34%

decreased by 0.58%

1 Month

12.04%

increased by 0.12%

Analysis last updated: Wednesday, September 30, 2026 at 05:04 PM UTC

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Date Range:

from

09/30/2024

to

09/30/2026

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

All

graph of PSI 20 Portuguese Stock Index GAS-GARCH-T

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Dec 30, 1992 to Sep 25, 2026

Model Insight

With persistence 0.994, volatility shocks have a half-life of 122 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 = 6.74 degrees of freedom, capturing fatter tails than a normal distribution.

𝑓

GAS-GARCH-T Model

Tap to view equation

High persistence: persistence 0.994, shock half-life ~122 daysv = 6.74 · fat tails
ParamValuet-stat
ωconst1.9923
1.37
αARCH0.0962
14.75***
βGARCH0.9943
244.07***
νDF6.7393
3.12***

0.994

Persistence

122d

Half-life
𝑓

GAS-GARCH-T Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

1.9923
1.37
α

ARCH

Response to squared shocks

0.0962
14.75***
β

GARCH

Volatility persistence

0.9943
244.07***
ν

DF

Student-t tail thickness

6.7393
3.12***

Persistence:

0.994

Half-life:

122 days