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S&P 500 Index GJR-GARCH Volatility Analysis

Volatility prediction for Monday, September 28th, 2026

1 Day

10.40%

decreased by 0.29%

1 Week

10.71%

increased by 0.02%

1 Month

11.75%

increased by 1.06%

Analysis last updated: Saturday, September 26, 2026 at 12:55 AM UTC

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graph of S&P 500 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
ωconst0.0216
5.16***
αARCH0.0034
0.35
βGARCH0.8973
104.26***
γleverage0.1602
7.46***

0.981

Persistence

36d

Half-life
σ

GJR-GARCH Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

0.0216
5.16***
α

ARCH

Response to squared shocks

0.0034
0.35
β

GARCH

Volatility persistence

0.8973
104.26***
γ

leverage

Additional response to negative shocks

0.1602
7.46***

Persistence:

0.981

Half-life:

36 days