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
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Oct 31, 1994 to Aug 14, 2026Model 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
| Parameter | Value | t-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
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