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Ishares S&P 500 EX S&P 1 ETF GJR-GARCH Volatility Analysis

Volatility prediction for Tuesday, September 29th, 2026

1 Day

11.83%

increased by 0.20%

1 Week

11.97%

increased by 0.34%

1 Month

12.35%

increased by 0.72%

Analysis last updated: Monday, September 28, 2026 at 09:57 PM UTC

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graph of Ishares S&P 500 EX S&P 1 ETF GJR-GARCH

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Jul 9, 2025 to Sep 25, 2026

Model Insight

Volatility shocks decay with a half-life of 11 trading days, meaning a shock loses half its impact after approximately 11 days.

σ

GJR-GARCH Model

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Shock decay: Shocks decay with a 11-day half-life
ParamValuet-stat
ωconst0.0401
0.78
αARCH0.0000
0.00
βGARCH0.8897
7.57***
γleverage0.1016
1.10

0.940

Persistence

11d

Half-life
σ

GJR-GARCH Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

0.0401
0.78
α

ARCH

Response to squared shocks

0.0000
0.00
β

GARCH

Volatility persistence

0.8897
7.57***
γ

leverage

Additional response to negative shocks

0.1016
1.10

Persistence:

0.940

Half-life:

11 days