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S&P Total Market Index GAS-GARCH Student T Volatility Analysis

Volatility prediction for Friday, October 23rd, 2026

1 Day

13.64%

increased by 1.54%

1 Week

13.82%

increased by 1.72%

1 Month

14.45%

increased by 2.35%

Analysis last updated: Thursday, October 22, 2026 at 11:08 PM UTC

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Date Range:

from

10/22/2024

to

10/22/2026

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

All

graph of S&P Total Market Index GAS-GARCH-T

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Mar 30, 2006 to Oct 16, 2026

Model Insight

Volatility shocks decay with a half-life of 40 trading days, meaning a shock loses half its impact after approximately 40 days. Returns follow a Student-t distribution with v = 6.75 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 40-day half-lifev = 6.75 · fat tails
ParamValuet-stat
ωlong-run1.3329
1.77*
αscore0.1080
8.16***
βpersistence0.9830
93.73***
νDF6.7496
1.79*

0.983

Persistence

40d

Half-life
𝑓

GAS-GARCH-T Model

Tap to view equation

ParameterValuet-statistic
ω

long-run

Long-run variance given a price move

1.3329
1.77*
α

score

Weight on the scaled score

0.1080
8.16***
β

persistence

Volatility persistence

0.9830
93.73***
ν

DF

Student-t tail thickness

6.7496
1.79*

Persistence:

0.983

Half-life:

40 days