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S&P Composite 1500 Index GAS-GARCH Student T Volatility Analysis

Volatility prediction for Monday, September 21st, 2026

1 Day

12.90%

decreased by 0.81%

1 Week

13.05%

decreased by 0.66%

1 Month

13.59%

decreased by 0.12%

Analysis last updated: Saturday, September 19, 2026 at 12:02 AM UTC

Date Range:

from

to

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

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graph of S&P Composite 1500 Index GAS-GARCH-T

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Oct 31, 1994 to Sep 18, 2026

Model Insight

Volatility shocks decay with a half-life of 58 trading days, meaning a shock loses half its impact after approximately 58 days. Returns follow a Student-t distribution with v = 7.56 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 58-day half-lifev = 7.56 · fat tails
ParamValuet-stat
ωconst1.3184
1.80*
αARCH0.0921
9.56***
βGARCH0.9881
134.56***
νDF7.5619
1.74*

0.988

Persistence

58d

Half-life
𝑓

GAS-GARCH-T Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

1.3184
1.80*
α

ARCH

Response to squared shocks

0.0921
9.56***
β

GARCH

Volatility persistence

0.9881
134.56***
ν

DF

Student-t tail thickness

7.5619
1.74*

Persistence:

0.988

Half-life:

58 days