Skip to main content
V-Lab
V-Lab

CBOE S&P 500 9-Day Volatility Index GAS-GARCH Student T Volatility Analysis

Volatility prediction for Tuesday, September 15th, 2026

1 Day

238.96%

increased by 4.95%

1 Week

224.95%

decreased by 9.06%

1 Month

207.15%

decreased by 26.86%

Analysis last updated: Tuesday, September 15, 2026 at 03:41 PM UTC

Date Range:

from

to

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

All

graph of CBOE S&P 500 9-Day Volatility Index GAS-GARCH-T

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Jan 3, 2011 to Sep 11, 2026

Model Insight

Volatility shocks decay with a half-life of 3 trading days, meaning a shock loses half its impact after approximately 3 days. Returns follow a Student-t distribution with v = 5.24 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 3-day half-lifev = 5.24 · fat tails
ParamValuet-stat
ωconst155.4384
4.89***
αARCH0.1138
2.69***
βGARCH0.7727
12.83***
νDF5.2381
0.80

0.773

Persistence

3d

Half-life
𝑓

GAS-GARCH-T Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

155.4384
4.89***
α

ARCH

Response to squared shocks

0.1138
2.69***
β

GARCH

Volatility persistence

0.7727
12.83***
ν

DF

Student-t tail thickness

5.2381
0.80

Persistence:

0.773

Half-life:

3 days