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Tokyo Stock Exchange Tokyo Stock Price Index TOPIX GAS-GARCH Student T Volatility Analysis

Volatility prediction for Friday, September 25th, 2026

1 Day

12.12%

decreased by 0.23%

1 Week

12.58%

increased by 0.23%

1 Month

14.05%

increased by 1.70%

Analysis last updated: Friday, September 25, 2026 at 05:41 PM UTC

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graph of Tokyo Stock Exchange Tokyo Stock Price Index TOPIX GAS-GARCH-T

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Jan 2, 1990 to Sep 22, 2026

Model Insight

Volatility shocks decay with a half-life of 32 trading days, meaning a shock loses half its impact after approximately 32 days. Returns follow a Student-t distribution with v = 6.31 degrees of freedom, capturing fatter tails than a normal distribution.

𝑓

GAS-GARCH-T Model

Tap to view equation

Shock decay: Shocks decay with a 32-day half-lifev = 6.31 · fat tails
ParamValuet-stat
ωconst1.6436
2.92***
αARCH0.0827
9.61***
βGARCH0.9784
127.88***
νDF6.3138
2.04**

0.978

Persistence

32d

Half-life
𝑓

GAS-GARCH-T Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

1.6436
2.92***
α

ARCH

Response to squared shocks

0.0827
9.61***
β

GARCH

Volatility persistence

0.9784
127.88***
ν

DF

Student-t tail thickness

6.3138
2.04**

Persistence:

0.978

Half-life:

32 days