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S&P 100 Index GJR-GARCH Volatility Analysis

Volatility prediction for Monday, September 28th, 2026

1 Day

10.57%

decreased by 0.27%

1 Week

10.87%

increased by 0.03%

1 Month

11.88%

increased by 1.04%

Analysis last updated: Saturday, September 26, 2026 at 12:53 AM UTC

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graph of S&P 100 Index GJR-GARCH

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Jan 1, 1990 to Sep 25, 2026

Model Insight

This asset exhibits a strong leverage effect: volatility responds almost entirely to negative shocks. The ARCH response to positive shocks is negligible.

σ

GJR-GARCH Model

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Leverage: volatility responds almost entirely to negative shocks
ParamValuet-stat
ωconst0.0209
4.93***
αARCH0.0049
0.53
βGARCH0.9020
94.25***
γleverage0.1507
6.97***

0.982

Persistence

39d

Half-life
σ

GJR-GARCH Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

0.0209
4.93***
α

ARCH

Response to squared shocks

0.0049
0.53
β

GARCH

Volatility persistence

0.9020
94.25***
γ

leverage

Additional response to negative shocks

0.1507
6.97***

Persistence:

0.982

Half-life:

39 days