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V-Lab

JSE Securities South African Volatility Index GAS-GARCH Student T Volatility Analysis

Volatility prediction for Friday, July 31st, 2026

1 Day

391.43%

decreased by 14.87%

1 Week

391.09%

decreased by 15.21%

1 Month

389.72%

decreased by 16.58%

Analysis last updated: Friday, July 31, 2026 at 08:05 PM UTC

Date Range:

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graph of JSE Securities South African Volatility Index GAS-GARCH-T

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Feb 1, 2007 to Apr 4, 2025

Model Insight

With persistence 0.999, volatility shocks have a half-life of 693 trading days (~2.7 years), close to a unit root, so long-run forecasts are highly sensitive to this estimate. Returns follow a Student-t distribution with v = 2.15 degrees of freedom, capturing fatter tails than a normal distribution.

𝑓

GAS-GARCH-T Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

72.2837
14.45***
α

ARCH

Response to squared shocks

0.0497
89.61***
β

GARCH

Volatility persistence

0.9990
ν

DF

Student-t tail thickness

2.1501
3,765.56***

Persistence:

0.999

Half-life:

693 days