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S&P 500 Equal Weight Index (EWI) MEM Volatility Analysis

Volatility prediction for Monday, September 14th, 2026

1 Day

9.39%

decreased by 0.78%

1 Week

9.95%

decreased by 0.22%

1 Month

11.72%

increased by 1.55%

Analysis last updated: Saturday, September 12, 2026 at 12:53 AM UTC

Date Range:

from

to

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

All

graph of S&P 500 Equal Weight Index (EWI) MEM

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Apr 25, 2003 to Sep 11, 2026

Model Insight

Volatility shocks decay with a half-life of 33 trading days, meaning a shock loses half its impact after approximately 33 days.

μ

MEM Model

Tap to view equation

Shock decay: Shocks decay with a 33-day half-life
ParamValuet-stat
ωconst0.0296
2.97***
αARCH0.2476
13.71***
βGARCH0.7314
51.03***

0.979

Persistence

33d

Half-life
μ

MEM Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

0.0296
2.97***
α

ARCH

Response to squared shocks

0.2476
13.71***
β

GARCH

Volatility persistence

0.7314
51.03***

Persistence:

0.979

Half-life:

33 days