What Are Forward Rates?

In the fixed income world, forward rates represent the market’s expectation of future interest rates. These are not observed directly but are derived from the yield curve. For instance, a 1-year rate starting 2 years from now—commonly called a “2y1y” forward—is implied from spot rates and used to project future borrowing costs or value interest rate derivatives.

Forward rates are marginal—they describe the price of taking risk at a specific point in time rather than across a full horizon.

Understanding Local Volatility

In options trading, local volatility plays a similar marginal role. It is a function of both the underlying price and time and tells us what the model assumes volatility will be if the underlying reaches a specific level at a specific point in the future.

Rather than describing the average volatility over time, local volatility isolates the instantaneous volatility at a given point. This allows for nuanced modeling of option prices and enables replication of the implied volatility surface using a deterministic model, such as the one described by the Dupire equation.

The Analogy: Local Volatility as Forward Volatility

The analogy becomes clearer when we compare a yield curve with an implied volatility surface:

  • The yield curve gives us the term structure of interest rates; from it, we derive forward rates.
  • The volatility surface maps implied volatility across strikes and maturities; from this, we extract local volatility.

In both cases, the derived values—forward rates and local vols—represent the marginal pricing of risk at specific intervals.

Just as forward rates allow for the pricing of forward-starting instruments and swaps, local volatility allows for the pricing of path-dependent options whose payoffs depend on how and when the underlying reaches certain levels.

Visualizing the Concept

This chart highlights the conceptual similarity between forward rates (used in bond markets) and forward-looking volatility (captured through local volatility). In both, we observe how expectations shift over time and how risk is priced differently at each maturity.

Why This Analogy Matters

This comparison isn’t just academic. It has direct applications for:

  • Hedging: Forward rates inform interest rate hedging strategies; local volatility informs vega and skew-sensitive hedges.
  • Pricing Exotics: Path-dependent instruments like cliquets, lookbacks, or barriers are better modeled using local volatility frameworks.
  • Model Calibration: Just as traders bootstrap the forward curve from observed bond prices, local vol models are calibrated to replicate observed market prices across strikes and maturities.

Moreover, understanding the analogy helps traders anticipate how changes in the volatility surface impact option values—especially in regions where options are close to being at-the-money.

Limitations of the Analogy

While helpful, the analogy is not perfect. Forward rates assume deterministic evolution in many models, while local volatility often serves as a proxy within a broader stochastic environment. Market behavior, particularly during stress periods, can challenge these assumptions, leading to discrepancies between modeled and realized outcomes.

Nonetheless, thinking of local volatility as a “volatility forward rate” remains a powerful tool in a trader’s conceptual arsenal.

Conclusion: A Bridge Between Risk Markets

By framing local volatility as the options-market counterpart to forward rates, we gain not only a better understanding of how options prices are constructed but also a framework for designing better trading strategies. This mental model helps bridge the gap between interest rate derivatives and equity or FX options, making volatility trading more intuitive for those with a background in rates—and vice versa.

This analogy is not just theory; it’s a practical guide to navigating volatility with precision.