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V-Lab

CBOE S&P 500 9-Day Volatility Index Asy. Power MEM Volatility Analysis

Volatility prediction for Tuesday, July 21st, 2026

1 Day

227.65%

decreased by 5.92%

1 Week

221.28%

decreased by 12.29%

1 Month

205.02%

decreased by 28.55%

Analysis last updated: Tuesday, July 21, 2026 at 12:02 PM UTC

Date Range:

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to

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graph of CBOE S&P 500 9-Day Volatility Index APMEM

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Oct 4, 2013 to Jul 17, 2026

Model Insight

This asset shows a rare inverse leverage effect: positive returns raise next-day volatility 155% more than negative returns. Volatility rises more after gains than after losses, the reverse of the usual leverage effect and uncommon among risky assets. The volatility power δ = 1.04 sits below 2, so large shocks influence volatility less than quadratically, a more outlier-robust response than standard GARCH.

μ

APMEM Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

0.8754
7.42***
α

ARCH

Response to squared shocks

0.1583
28.31***
β

GARCH

Volatility persistence

0.8019
111.97***
γ

leverage

Additional response to negative shocks

-0.4234
-20.66***
δ

power

Transformation power

1.0367
21.39***

Persistence:

0.929

Half-life:

9 days