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S&P 500 Index Zero Slope Spline-GARCH Volatility Analysis

Volatility prediction for Tuesday, October 13th, 2026

1 Day

11.11%

decreased by 0.35%

1 Week

11.60%

increased by 0.14%

1 Month

13.06%

increased by 1.60%

Analysis last updated: Tuesday, October 13, 2026 at 12:07 AM UTC

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Date Range:

from

10/12/2024

to

10/12/2026

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

All

graph of S&P 500 Index S0GARCH

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Jan 1, 1990 to Oct 9, 2026

Model Insight

This model fits a time-varying baseline (a spline), so volatility mean-reverts toward a slowly-shifting long-run level rather than a constant. Short-run deviations decay with a half-life of 21 trading days.

τ

Zero Slope Spline-GARCH Model

Tap to view equation

Time-varying baseline: volatility reverts to a slowly-shifting spline trend
ParamValuet-stat
ωconst1.3797
7.84***
αARCH0.1021
10.27***
βGARCH0.8659
74.48***
∑γi Spline Coefficients
K=6
γ10.0858
6.63***
γ2-0.1358
-6.43***
γ30.0771
4.85***
γ4-0.0467
-3.31***
γ50.0395
2.48**
γ6-0.0288
-2.32**

0.968

Persistence

21d

Half-life
τ

Zero Slope Spline-GARCH Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

1.3797
7.84***
α

ARCH

Response to squared shocks

0.1021
10.27***
β

GARCH

Volatility persistence

0.8659
74.48***
∑γi Spline Coefficients
K=6
γ10.0858
6.63***
γ2-0.1358
-6.43***
γ30.0771
4.85***
γ4-0.0467
-3.31***
γ50.0395
2.48**
γ6-0.0288
-2.32**

Persistence:

0.968

Half-life:

21 days