V-Lab
State Street SPDR S&P Biotech ETF APARCH Volatility Analysis
Volatility prediction for Wednesday, September 16th, 2026
1 Day
30.05%
1 Week
30.10%
1 Month
30.30%
Analysis last updated: Tuesday, September 15, 2026 at 11:10 PM UTC
News Impact Curve
How returns affect tomorrow's volatilityVolatility Forecast
How volatility evolves over timeParameter Estimates
Feb 6, 2006 to Sep 11, 2026Model Insight
This asset exhibits a strong leverage effect: volatility responds almost entirely to negative shocks. The ARCH response to positive shocks is negligible. The volatility power δ = 1.30 sits below 2, so large shocks influence volatility less than quadratically, a more outlier-robust response than standard GARCH.
APARCH Model
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| Param | Value | t-stat |
|---|---|---|
| ωconst | 0.0549 | 5.21*** |
| αARCH | 0.0662 | 6.06*** |
| βGARCH | 0.9190 | 88.55*** |
| γleverage | 0.5672 | 5.24*** |
| δpower | 1.2998 | 6.79*** |
0.977
Persistence30d
Half-lifeAPARCH Model
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| Parameter | Value | t-statistic |
|---|---|---|
ω const Unconditional variance weight | 0.0549 | 5.21*** |
α ARCH Response to squared shocks | 0.0662 | 6.06*** |
β GARCH Volatility persistence | 0.9190 | 88.55*** |
γ leverage Additional response to negative shocks | 0.5672 | 5.24*** |
δ power Transformation power | 1.2998 | 6.79*** |
Persistence:
0.977
Half-life:
30 days
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