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V-Lab

Vanguard S&P 500 Index ETF GAS-GARCH Student T Volatility Analysis

Volatility prediction for Monday, July 27th, 2026

1 Day

12.83%

decreased by 1.03%

1 Week

12.93%

decreased by 0.93%

1 Month

13.24%

decreased by 0.62%

Analysis last updated: Saturday, July 25, 2026 at 09:14 AM UTC

Date Range:

from

to

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

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graph of Vanguard S&P 500 Index ETF GAS-GARCH-T

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Nov 8, 2012 to Jul 24, 2026

Model Insight

Volatility shocks decay with a half-life of 14 trading days, meaning a shock loses half its impact after approximately 14 days. Returns follow a Student-t distribution with v = 9.10 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

0.7691
16.70***
α

ARCH

Response to squared shocks

0.1114
21.21***
β

GARCH

Volatility persistence

0.9510
257.79***
ν

DF

Student-t tail thickness

9.0950
3.61***

Persistence:

0.951

Half-life:

14 days