Implied Volatility — The Price of Optionality

Implied volatility (IV) is the option market's estimate of how much the underlying will move between now and the option's expiration, expressed as an annualized standard deviation of log returns. The name is somewhat misleading: IV is not a forecast of realized volatility, nor is it a measure of how much the option's price will change. It is a parameter in the Black-Scholes formula that, when solved for, produces the option's current market price.

IV vs. realized volatility

Realized volatility is the actual standard deviation of the underlying's returns over a historical period (typically 10, 20, or 30 trading days). Implied volatility is the option market's estimate of the future realized volatility. The two are related but not the same: realized volatility is what happened, implied volatility is what the market thinks will happen.

The relationship between IV and realized volatility is the basis for every options trade. If IV is higher than realized volatility, the option is "expensive" — the market is pricing more movement than the underlying has actually delivered. If IV is lower than realized volatility, the option is "cheap" — the market is pricing less movement than the underlying has actually delivered. The journal's playbook is built around the assumption that IV tends to mean-revert to realized volatility over time, which means selling high IV and buying low IV has a structural edge.

IV rank

IV rank is the option market's standardized measure of how high or low the current IV is relative to the underlying's IV history. The formula is:

IV Rank = (Current IV - 52-Week Low IV) / (52-Week High IV - 52-Week Low IV) × 100

The result is a percentage between 0 and 100. An IV rank of 0 means the current IV is at its 52-week low; an IV rank of 100 means the current IV is at its 52-week high. The journal uses IV rank to decide which structures to deploy:

• IV rank > 50 — Sell premium. The option market is pricing more movement than the underlying has historically delivered, so selling premium (credit spreads, iron condors, covered calls) has a structural edge. The journal opens short-premium structures at IV rank > 50 and avoids long-premium structures at high IV.
• IV rank < 25 — Buy premium. The option market is pricing less movement than the underlying has historically delivered, so buying premium (debit spreads, long calls, long puts) is cheaper than usual. The journal opens long-premium structures at IV rank < 25 and avoids short-premium structures at low IV.
• IV rank 25-50 — Neutral. The market is pricing roughly the historical average movement, and the choice of structure depends on the directional thesis rather than the IV regime.

The IV rank thresholds are not hard rules. The journal has opened short-premium structures at IV rank 30 when the directional thesis was clearly neutral, and has opened long-premium structures at IV rank 60 when the directional thesis was clearly directional. The IV rank is one input among several, not a decision in itself.

Volatility smile and skew

The IV is not constant across strikes. The shape of the IV across strikes for a given expiration is called the volatility smile (or skew, depending on the shape). For SPX, the smile is typically downward-sloping on the put side: out-of-the-money puts have higher IV than at-the-money options, and out-of-the-money calls have lower IV. The shape reflects the market's pricing of tail risk — the market is more worried about a sharp decline than a sharp rally.

The journal uses the skew in two ways:

1. Strike selection on spreads. For a credit spread, the journal prefers to sell the short strike on the side of the smile where the IV is higher. A bull put spread on SPX sells a put at a strike where the IV is elevated (the put side of the smile), and the credit collected is higher than it would be at a strike closer to the money. The trade-off is that the probability of profit is also lower, which the journal weighs against the higher credit.
2. Risk-reversal structures. The journal occasionally opens risk reversals (long call + short put) to take advantage of the skew. The structure is delta-neutral at entry, and the cost is the difference between the call's premium and the put's premium. On SPX, the put is more expensive than the equivalent call, so the risk reversal is a net credit. The journal uses the risk reversal as a low-cost directional bet when the directional thesis is clear.

Vega and IV

Vega is the option greek that measures the sensitivity of the option's price to a 1% change in IV. A long option has positive vega; a short option has negative vega. The iron butterfly has negative vega (the position is hurt by an IV expansion); the iron condor has negative vega; the long call has positive vega.

The journal monitors the vega of every position at entry. A long call with a high vega is a position that benefits from an IV expansion — the journal will open this position when the IV rank is low and the directional thesis is clear. A short call spread with a high negative vega is a position that benefits from an IV contraction — the journal will open this position when the IV rank is high and the directional thesis is neutral.

The vega of a position changes over time. As the option approaches expiration, the vega decreases (the option's price becomes less sensitive to IV changes). The journal accounts for the vega decay in the position's expected value: a short-premium position that is opened at high IV and held to expiration will benefit from both the theta decay and the vega decay, while a long-premium position will benefit from the directional move but lose some of its value to the vega decay.

IV crush

IV crush is the rapid decline in IV that occurs after a known event (earnings, FOMC release, macro data print). The IV is highest before the event because the option market is pricing the uncertainty of the event; once the event is over, the IV drops to the post-event level. The drop in IV is sometimes called the "IV crush" because it can be large and fast.

The journal trades around IV crush in two ways:

1. Pre-event premium selling. The journal sometimes opens short-premium positions before a known event (FOMC, CPI), collecting the elevated IV before the crush. The risk is that the underlying moves more than the structure can absorb, in which case the position loses. The journal sizes these positions to 1% of NLV rather than the usual 2% because the move risk is higher than usual.
2. Post-event directional buying. The journal sometimes opens long-premium positions after a known event, when the IV has crushed and the directional thesis is clear. The structure is typically a debit vertical (long call vertical for a bullish thesis, long put vertical for a bearish thesis). The advantage of buying after the event is that the IV is lower, so the debit is cheaper; the disadvantage is that the directional move has already happened, and the thesis is usually less clear.

The journal does not trade the event itself. The IV crush is a real phenomenon, but the move risk around the event is high, and the journal's playbook is built around defined-risk structures that benefit from the time decay between events, not from the gap moves that occur during events.