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V-Lab

S&P Composite 1500 Index APARCH Volatility Analysis

Volatility prediction for Thursday, August 20th, 2026

1 Day

13.63%

decreased by 0.86%

1 Week

13.93%

decreased by 0.56%

1 Month

14.94%

increased by 0.45%

Analysis last updated: Thursday, August 20, 2026 at 12:04 AM UTC

Date Range:

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to

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

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graph of S&P Composite 1500 Index APARCH

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Oct 31, 1994 to Aug 14, 2026

Model Insight

Volatility shocks decay with a half-life of 26 trading days, meaning a shock loses half its impact after approximately 26 days. The volatility power δ = 1.00 sits below 2, so large shocks influence volatility less than quadratically, a more outlier-robust response than standard GARCH.

σ

APARCH Model

Tap to view equation

ParameterValuet-statistic
ω

const

Unconditional variance weight

0.0319
36.86***
α

ARCH

Response to squared shocks

0.0856
26.60***
β

GARCH

Volatility persistence

0.9055
362.78***
γ

leverage

Additional response to negative shocks

1.0000
18.70***
δ

power

Transformation power

1.0047
40.70***

Persistence:

0.974

Half-life:

26 days