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
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Jan 1, 1990 to Sep 18, 2026Model 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
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Shock decay: Shocks decay with a 39-day half-life
| Param | Value | t-stat |
|---|---|---|
| ωconst | 0.0234 | 3.01*** |
| αARCH | 0.2214 | 14.58*** |
| βGARCH | 0.7609 | 68.21*** |
0.982
Persistence39d
Half-lifeμ
MEM Model
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| Parameter | Value | t-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
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