Rho — Concept Explainer Video

Transcript

The cost of money matters

Rho estimates how option value changes when the interest rate input changes, with other inputs fixed. Think of it as sensitivity to the cost of carrying and financing exposure through time. It is often less noticeable in short dated stock options.

A percentage point example

Suppose a European stock call has rho of twenty cents per interest rate percentage point. If the model rate rises from four to five percent, its estimated value rises twenty cents per share. For a one hundred multiplier, that is twenty dollars.

Calls and puts can respond differently

For standard European stock option models, purchased calls generally have positive rho and purchased puts negative rho. Longer maturities often increase rate sensitivity. These signs should not be carried blindly into every futures, currency, or interest rate option model.

Rho is not the whole market response

A central bank announcement can change stock prices and implied volatility as well as rates. Rho isolates only the rate input effect. It does not forecast the total profit or loss from that announcement.

Know the convention

Check whether rho is per percentage point or per basis point, and whether it is per unit or contract. One percentage point is one hundred basis points. Use matching units and evaluate the full position when rates change.