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V-Lab
V-Lab

S&P 500 Index MEM Volatility Analysis

Volatility prediction for Friday, September 25th, 2026

1 Day

11.41%

decreased by 0.36%

1 Week

11.72%

decreased by 0.05%

1 Month

12.75%

increased by 0.98%

Analysis last updated: Friday, September 25, 2026 at 12:03 AM UTC

Date Range:

from

to

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

All

graph of S&P 500 Index MEM

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Jan 1, 1990 to Sep 18, 2026

Model Insight

Volatility shocks decay with a half-life of 39 trading days, meaning a shock loses half its impact after approximately 39 days.

μ

MEM Model

Tap to view equation

Shock decay: Shocks decay with a 39-day half-life
ParamValuet-stat
ωconst0.0234
3.01***
αARCH0.2214
14.58***
βGARCH0.7609
68.21***

0.982

Persistence

39d

Half-life
μ

MEM Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

0.0234
3.01***
α

ARCH

Response to squared shocks

0.2214
14.58***
β

GARCH

Volatility persistence

0.7609
68.21***

Persistence:

0.982

Half-life:

39 days