The beginner track introduced the idea that bond prices fall when rates rise. Duration turns that intuition into a number you can actually use.
A measure of sensitivity
Duration estimates how much a bond’s price moves for a 1% change in interest rates. A bond with a duration of 7 will fall roughly 7% if yields rise 1%, and rise roughly 7% if yields fall 1%. It’s the single most useful gauge of a bond’s interest-rate risk.
(Confusingly, duration is quoted in years — it began as a measure of the average time to receive a bond’s cash flows — but for our purposes treat it as the % price move per 1% yield move, which is what “modified duration” gives you.)
What drives it
Duration is higher — meaning more rate risk — when a bond has:
- a longer maturity (more years of payments exposed to rate changes),
- a lower coupon (more of its value sits in the distant final payment), and
- a lower yield.
This is why a 30-year zero-coupon bond is brutally sensitive to rates, while a 2-year bond barely flinches — exactly the asymmetry the diagram shows.
Worked example
You hold a bond worth $10,000 with a duration of 7. Interest rates rise 1% (100 basis points):
Price change ≈ −duration × rate change = −7 × 1% = −7%
So the bond drops about $700, to ~$9,300. If instead rates fell 1%, it would rise ~$700. Now compare a short bond with a duration of 2: the same 1% move shifts it only ~$200. Same rate change, very different pain — that’s duration in dollars.
Why it matters
Duration lets you dial your rate risk up or down on purpose. Worried rates will rise? Hold shorter-duration bonds to cushion the hit. Expect rates to fall? Longer-duration bonds will gain the most. It also lets you compare the rate risk of very different bonds on one scale.
The takeaway
Duration is the number that quantifies a bond’s interest-rate risk — roughly the % price move per 1% change in yield. Longer maturity and lower coupons mean higher duration and bigger swings. It’s the lever you use to manage rate risk. (This is education, not investment advice.)