The Maturity Effect:
When Longer Doesn't Mean More Sensitive

📅 2026 ⏱ 6 min read 📊 Interactive widget included

The rule you already know

Duration measures a bond's sensitivity to interest rate changes. The longer a bond's maturity, the longer investors must wait for cash flows — which makes those cash flows more sensitive to discounting. So the general rule holds: longer maturity → higher duration → greater price sensitivity.
The Maturity Effect
"Holding coupon rate and yield-to-maturity constant, an increase in a bond's time to maturity will generally increase its Macaulay duration. This is called the maturity effect."
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The exception

The maturity effect can fail for bonds that satisfy all three of these conditions simultaneously:
Condition 1
Low coupon
Below the yield-to-maturity — but not zero. Zero-coupon bonds are always exempt from this exception.
Condition 2
Long maturity
The effect only appears at very long maturities — typically beyond 20–30 years, depending on the coupon and yield.
Condition 3
Trading at discount
The bond's price must be below par — meaning the coupon is lower than the yield-to-maturity.
When all three conditions are met, adding more years to maturity can actually decrease the bond's duration — the opposite of what intuition suggests.
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Why does this happen?

Think of duration as a tug-of-war between two forces:
↑ pushes duration up
⏳
Time effect
Longer maturity means cash flows arrive later, so duration naturally increases. This is the dominant force in most bonds.
vs
↓ pulls duration down
🧲
Pull-to-par effect
A discount bond is pulled toward face value as it matures. For deeply discounted bonds, this acceleration of value recovery is like receiving an early cash flow — which pulls duration downward.
For normal bonds, the time effect wins. But for a low-coupon, long-term, deeply discounted bond , the pull-to-par force becomes so strong that it overrides the time effect — causing duration to fall as maturity lengthens beyond a certain threshold.

"A zero-coupon bond has no coupons to create the pull-to-par dynamic. Its duration always equals its maturity exactly — so the exception never applies to zeros."

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Illustrative example - Explore it yourself

Use the widget below to see exactly when the exception appears. Try setting the coupon to 1% and YTM to 8% to reproduce the table above — then raise the coupon toward 6% and watch the curve become monotonically increasing again.
Bond Duration Explorer — RUQQI Interactive
1.0%
8.0%
Bond trades at
Discount
Perpetuity ceiling
12.50 yr
Exception visible
Yes ⚠
⚠ Exception active: modified duration peaks then falls as maturity increases — the maturity effect breaks down.
Maturity Price ($) Mac. Duration Mod. Duration vs Previous Status
Annual coupon · Face value $1,000 · Macaulay duration = Σ[t × PV(CFt)] ÷ Price · Modified duration = Mac. duration ÷ (1 + YTM)
Fix coupon at 1% and YTM at 8%. The bond is trading at deep discount to Par. We notice the following:
"At the 40-year mark, modified duration plateaus at 18.04 years — the same as the 30-year bond — and then actually falls to 16.66 years at 50 years, a drop of 1.39 years. This is a clear violation of the maturity effect."
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KEY TAKEAWAYS

  • Longer maturity → higher duration: true almost always.
  • The exception requires three conditions at once: low coupon + long maturity + discount price.
  • Zero-coupon bonds: no exception. Duration = maturity, always.
  • Even when the exception occurs, duration eventually recovers toward 1/YTM as maturity → ∞.