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V-Lab

Vanguard S&P 500 Index ETF APARCH Volatility Analysis

Volatility prediction for Wednesday, July 15th, 2026

1 Day

12.21%

decreased by 0.34%

1 Week

12.51%

decreased by 0.04%

1 Month

13.37%

increased by 0.82%

Analysis last updated: Wednesday, July 15, 2026 at 09:11 AM UTC

Date Range:

from

to

6M ·

1Y ·

2Y ·

5Y ·

10Y ·

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graph of Vanguard S&P 500 Index ETF APARCH

News Impact Curve

How returns affect tomorrow's volatility

Volatility Forecast

How volatility evolves over time

Parameter Estimates

Nov 8, 2012 to Jul 10, 2026

Model Insight

Volatility shocks decay with a half-life of 13 trading days, meaning a shock loses half its impact after approximately 13 days. The volatility power δ = 1.26 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

0.0497
24.36***
α

ARCH

Response to squared shocks

0.0819
1.58
β

GARCH

Volatility persistence

0.8669
183.17***
γ

leverage

Additional response to negative shocks

1.0000
1.02
δ

power

Transformation power

1.2581
29.77***

Persistence:

0.947

Half-life:

13 days