Definition
Duration is a measure of interest rate sensitivity—how much the price (or value) of a fixed-income instrument like a bond or loan is expected to change when interest rates (yields) move. In real estate, duration is most often used to understand and manage rate risk in real estate debt (mortgages, CMBS, mezzanine debt) and in portfolios that include bonds, rate hedges, or debt-like cash flows.
Two Common Meanings
Macaulay duration
Macaulay duration is the weighted-average time (in years) to receive a bond’s cash flows, where the weights are the present value of each cash flow. It’s most often a building block used to calculate modified duration.
Modified duration
Modified duration is the most commonly quoted “duration†in practice. It approximates the percentage price change of a bond (or loan) for a 1.00% (100 bps) change in yield:
- % Price Change (approx.) ≈ − Modified Duration × ΔYield
Example: if modified duration is 4.0 and yields rise by 1.00%, the price is expected to fall by roughly 4% (before considering convexity and other effects).
Why It Matters in Real Estate
- Debt pricing & refi risk: higher duration generally means the debt instrument’s value is more sensitive to rate changes, which can impact marks, spreads, and financing terms.
- Hedging decisions: duration helps size interest rate swaps, caps, floors, or Treasuries used to hedge rate exposure.
- Portfolio construction: investors often monitor “effective duration†across a portfolio of loans and fixed-income-like positions to limit overall rate sensitivity.
- Prepayment behavior: many real estate loans have call protection, yield maintenance, defeasance, or prepayment options that can change duration as rates move.
Duration vs. Loan Term
Duration is not the same as maturity or loan term. A 10-year loan can have a much shorter duration if it amortizes quickly, prepays early, or has cash flows concentrated earlier. Conversely, interest-only structures can have longer duration because more value is received later.
Types of Duration You’ll See
- Effective duration: incorporates the impact of embedded options (like prepayment).
- Spread duration: sensitivity to changes in credit spread (holding rates constant).
- Key rate duration: sensitivity to specific points on the yield curve (e.g., 2-year vs 10-year).
Example
A CMBS bond has a modified duration of 5.5. If yields increase by 0.50% (50 bps), the approximate price impact is:
- % Price Change ≈ −5.5 × 0.005 = −2.75%
In practice, the realized change may differ because of convexity, spread moves, and changes in prepayment/default expectations.
Common Pitfalls
- Ignoring convexity: duration is a first-order approximation; larger rate moves can deviate materially.
- Mixing rate and spread risk: a price move can be driven by Treasury rates, spreads, or both—use the right metric.
- Assuming duration is constant: options (prepay/call) can make duration change as rates move.
- Comparing across structures: IO, amortizing, floating-rate, and callable debt behave very differently.
Investor Uses
- Hedge sizing: estimate hedge notional for swaps/caps based on target duration exposure.
- Rate-risk limits: set portfolio constraints on effective duration and key-rate buckets.
- Scenario testing: model value changes under parallel shifts and curve steepening/flattening.
- Debt selection: compare floating-rate vs fixed-rate exposure when choosing financing.