Skip to main content
V-Lab
V-Lab

S&P Total Market Index Zero Slope Spline-GARCH Volatility Analysis

Volatility prediction for Monday, September 21st, 2026

1 Day

12.56%

decreased by 0.61%

1 Week

13.10%

decreased by 0.07%

1 Month

14.71%

increased by 1.54%

Analysis last updated: Saturday, September 19, 2026 at 12:02 AM UTC

Date Range:

from

to

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

All

graph of S&P Total Market Index S0GARCH

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Mar 30, 2006 to Sep 18, 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 20 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
ωconst0.8961
5.82***
αARCH0.1304
8.85***
βGARCH0.8354
49.63***
γi Spline Coefficients
K=3
γ1-0.0266
-2.25**
γ20.0485
2.72***
γ3-0.0302
-3.04***

0.966

Persistence

20d

Half-life
τ

Zero Slope Spline-GARCH Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

0.8961
5.82***
α

ARCH

Response to squared shocks

0.1304
8.85***
β

GARCH

Volatility persistence

0.8354
49.63***
γi Spline Coefficients
K=3
γ1-0.0266
-2.25**
γ20.0485
2.72***
γ3-0.0302
-3.04***

Persistence:

0.966

Half-life:

20 days