What is key rate duration and why is it better than effective duration for managing bond portfolios?

Key rate duration is one of the most practical risk measures for fixed-income portfolio managers, and it's heavily tested at CFA Level II. Here's the full picture.

Effective Duration: The Blunt Instrument

Effective duration tells you how much a bond's price changes for a parallel shift in the entire yield curve. For example, if a bond has an effective duration of 5.2, a 100bp parallel shift changes the price by approximately 5.2%.

But here's the problem: yield curves rarely shift in parallel. Short rates might rise while long rates fall (a flattening), or the belly might move independently.

Key Rate Duration: The Scalpel

Key rate duration decomposes interest rate sensitivity across specific maturities on the yield curve — typically 2Y, 5Y, 10Y, and 30Y. Each key rate duration tells you the bond's price sensitivity to a shift at that single point, holding all other rates constant.

Example:

Consider two bonds held by Glenridge Fixed Income Partners:

Both bonds have the same effective duration, but their risk profiles are completely different. Bond A is concentrated at the 10-year point, while Bond B has cash flows spread across the curve.

Why This Matters:

If you expect a curve flattening (short rates up, long rates down), Bond A would perform much better than Bond B, despite identical effective durations. A portfolio manager using only effective duration would see these as equivalent — a potentially costly mistake.

Practical Application:

Suppose you manage a liability-driven portfolio and your liabilities have key rate durations of KRD₂ = 1.0, KRD₁₀ = 4.5, KRD₃₀ = 3.0. You'd want to match assets to these specific key rate durations, not just match overall duration.

Exam Tip: When a CFA Level II vignette gives you key rate durations for two portfolios and asks about non-parallel yield curve shifts, calculate the price change at each maturity and sum them. Don't just use effective duration.

For more fixed-income practice, check our CFA Level II question bank.