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

Volatility prediction for Wednesday, August 26th, 2026

1 Day

11.28%

decreased by 0.55%

1 Week

11.59%

decreased by 0.24%

1 Month

12.63%

increased by 0.80%

Analysis last updated: Tuesday, August 25, 2026 at 11:06 PM UTC

Date Range:

from

to

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

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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 Aug 21, 2026

Model Insight

Volatility shocks decay with a half-life of 41 trading days, meaning a shock loses half its impact after approximately 41 days. Returns follow a Student-t distribution with v = 6.68 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

1.3463
6.94***
α

ARCH

Response to squared shocks

0.1082
32.58***
β

GARCH

Volatility persistence

0.9831
370.57***
ν

DF

Student-t tail thickness

6.6842
7.24***

Persistence:

0.983

Half-life:

41 days