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Summary

Vol-of-vol is the dispersion (standard deviation) of implied volatility itself — how much IV fluctuates around its own level over a given horizon (variance-based measures swap standard deviation of IV for dispersion of variance; this page uses the IV-standard-deviation convention). Just as IV can be quoted as an index (VIX for 30-day SPX IV), its own volatility is quoted as the CBOE VVIX Index, which measures the implied volatility of VIX options1. Vol-of-vol is invisible in single-option greeks yet dominates the tail behavior of short-vol strategies.

Definition and Measurement

Quantity Object Instrument
Realized vol (RV) Dispersion of the underlying Computed from returns
Implied vol (IV) Market's priced forward vol Option prices (VIX for SPX)
Vol-of-vol Dispersion of IV itself VIX options; CBOE VVIX index

VVIX is constructed like VIX but applied to the VIX options strip: it is the market's priced volatility of 30-day SPX implied volatility1. It typically ranges far higher than VIX itself (historically roughly 70–120+ vs. VIX's 10–80), reflecting the fat right tail of IV: vol can spike many multiples of its norm in days, but cannot fall far below its floor.

Why Short Vol Is Short Vol-of-Vol

A short-vol position (short strangles, condors, short VIX futures, short gamma) is not merely short the level of IV. Its P&L depends on how IV moves:

  • When IV rises sharply, option prices reprice against the seller immediately (vega loss), regardless of whether realized vol later justifies the level.
  • The speed of IV repricing scales with vol-of-vol: high vol-of-vol means IV can gap 10–20+ points in minutes (the earnings crush in reverse — an "IV rush" against the seller)1.
  • Short VIX-futures and VIX-call-buying flows embed the same exposure: these instruments are claims on IV, so their risk is IV's volatility.

Hence every short-vol book is implicitly short vol-of-vol — it is short the IV-spike convexity, losing disproportionately when IV gaps — even if its vega appears small at entry.

Regime-Risk Implications

Vol-of-vol is the mechanism that turns calm-regime premium harvesting into catastrophic tail loss:

  • Convexity mismatch: short-vol P&L is linear-to-concave on the downside; losses accelerate exactly when vol-of-vol spikes, forcing hedges at the worst prices.
  • Forced deleveraging: VIX ETPs and vol-targeting funds size off IV levels; an IV spike triggers mechanical buying of volatility, which feeds the spike — see VIX ETP flows.
  • Regime signal: elevated VVIX relative to VIX marks markets pricing uncertainty about uncertainty — a leading indicator worth tracking in any regime definition that gates short-vol sizing.

Status note (draft): the mechanism above is synthesized from index documentation rather than the four book bundles; verify against the CBOE VVIX white paper and empirical VIX/VVIX behavior before treating as settled. The books' treatment of vega (see vega) covers IV-level risk but not vol-of-vol convexity.

Practical Consequences for Strategy Design

  • Sizing: cap short-vol size off stressed vol-of-vol, not current IV — the loss distribution's tail is a vol-of-vol quantity, not an IV-level quantity.
  • Hedging: long wings (puts, VIX calls) are the direct hedge; they are cheap or rich precisely in proportion to the market's priced vol-of-vol.
  • Monitoring: track the VVIX/VIX ratio; sustained elevation signals the market pricing event risk that a level-only IV screen would miss.

Links

References

  1. CBOE Global Markets, VVIX — CBOE VIX Volatility Index white paper and index methodology, https://www.cboe.com/us/indices/dashboard/vvix/ (retrieved for verification). - CBOE, VIX White Paper (index construction for VIX and related volatility indexes), https://www.cboe.com/us/options/dashboard/vix/ - Carr, P. and Wu, L., "Volatility Risk Premiums," Review of Financial Studies 22(6), 2009 — academic treatment of volatility-of-volatility risk premia. ↩↩↩