Implied volatility is the most misunderstood number on an option chain, and the misunderstanding is always the same: people read it as a forecast.

It is not a forecast. It is an output — the volatility figure you have to feed a pricing model to make it agree with the price the market is already charging. IV does not tell you what will happen. It tells you what people are currently paying, expressed in a unit that lets you compare one contract to another.

The model, run backwards

A pricing model takes five inputs and produces a price. Four of the five are observable: the stock price, the strike, the time remaining and the interest rate. The fifth — volatility — is not.

So when a chain says a contract has 34% implied volatility, it means: at 34% annualised volatility, the model produces exactly the price the market is quoting. Change the market price and the implied volatility changes with it, because it is derived from the price rather than the other way round.

This has a useful consequence. IV is a normalised way to compare premium. A $3.00 contract on a $50 stock and a $9.00 contract on a $400 stock cannot be compared directly. Their implied volatilities can.

What actually moves it

Demand for options. Above all else. IV rises when people want contracts — typically protection — and falls when they do not. It is a price, and prices respond to demand.

Known upcoming events. Earnings, rulings, trial results. Uncertainty with a date attached inflates IV until the date passes, then it collapses. That collapse is IV crush, and it has its own lesson.

Recent realised movement. A stock that has been jumping around tends to have higher implied volatility, because participants extrapolate — sometimes correctly.

Market-wide fear. In a selloff, implied volatility rises across almost everything simultaneously. This is why correlation risk matters: your five separate short-premium positions all get marked against you on the same afternoon.

Why sellers care

As the vega lesson established, selling premium is structurally a short-volatility position. Higher IV means you collect more for the same strike, same expiration, same obligation.

Implied against realised

Realised volatility is how much the stock actually moved, measured after the fact. Implied volatility is what the market charged in advance. They are rarely equal.

Historically, implied has tended to run slightly above subsequent realised volatility across broad markets — the variance risk premium. That gap is the structural edge premium sellers are harvesting, and it is genuinely there. It is also modest, inconsistent, and entirely capable of disappearing for months while you are short.

The honest framing: sellers are paid a small persistent premium for absorbing volatility risk. It is an edge, not a guarantee, and it is smaller than most people selling premium believe.

Is 34% high?

On its own, that question has no answer. Thirty-four percent is low for a biotech and alarming for a utility. Absolute IV tells you nothing without context.

The context comes from comparing a stock's IV to its own history, which is what IV rank and IV percentile do — and where the next lesson picks up.

What can go wrong

Treating IV as a prediction. It is a price. Prices are frequently wrong in both directions.

Selling the highest IV you can find. The names with the richest premium are the ones the market is most worried about, and often correctly.

Comparing raw IV across different stocks. Compare each name to its own history instead.

Forgetting an event inside your expiration. Elevated IV frequently means an earnings date you did not check for.