One of the most important ideas in investing is also one of the most confusing at first:
When bond prices rise, bond yields fall. When bond prices fall, bond yields rise.
Why does this happen?
The easiest way to understand it is with a simple example.
Imagine You Buy a $1,000 Bond
Suppose the U.S. government issues a bond with:
- Face value: $1,000
- Annual interest payment: $50
- Coupon rate: 5%
If you buy the bond for exactly $1,000, you receive $50 every year.
Your yield is therefore:
$50 ÷ $1,000 = 5%
Simple enough.
But after the bond is issued, it can be bought and sold in the market. The $50 annual payment does not change, but the bond’s market price does.
That is where things become interesting.
What Happens When the Bond Price Rises?
Suppose interest rates in the economy fall.
Investors now find a bond paying $50 per year attractive, so they are willing to pay more for it.
The bond price rises from:
$1,000 → $1,100
But the bond still pays only $50 per year.
The approximate current yield becomes:
$50 ÷ $1,100 = 4.55%
So:
Bond price ↑
Bond yield ↓
You paid more money to receive the same $50 annual payment, so your return is lower.
What Happens When the Bond Price Falls?
Now imagine market interest rates rise.
New bonds may offer better returns, so investors are less interested in the old bond paying only $50 per year.
Its market price might fall to:
$900
It still pays $50 annually.
Now the approximate yield becomes:
$50 ÷ $900 = 5.56%
So:
Bond price ↓
Bond yield ↑
You are paying less money for the same $50 income stream, so your return is higher.
The Relationship at a Glance
| Bond Price | Annual Payment | Approx. Yield |
|---|---|---|
| $900 | $50 | 5.56% |
| $1,000 | $50 | 5.00% |
| $1,100 | $50 | 4.55% |
Notice that the $50 payment never changed.
Only the price investors were willing to pay changed.
That is the key to understanding the inverse relationship.
Why Do Bond Prices Change?
The biggest reason is changes in prevailing interest rates.
Suppose you own a bond paying 5%.
If newly issued bonds suddenly pay 6%, why would another investor pay full price for your old 5% bond?
They probably wouldn’t.
Your bond’s price has to fall until its effective return becomes competitive with newer bonds.
The opposite happens when new bonds pay only 4%.
Your old 5% bond suddenly becomes attractive, so investors may bid up its price.
This creates the fundamental relationship:
Market interest rates ↑ → Existing bond prices ↓
Market interest rates ↓ → Existing bond prices ↑
Why Government Bond Buying Can Lower Yields
This also explains why governments and central banks sometimes buy bonds during periods of financial stress.
Large-scale buying creates additional demand for bonds.
More demand can push:
Bond prices ↑
which automatically causes:
Bond yields ↓
Lower government bond yields can then influence mortgage rates, corporate borrowing costs, and many other interest rates throughout the economy.
However, this does not necessarily solve the reason investors originally demanded higher yields.
If investors are worried about inflation, government debt, deficits, or other risks, yields may eventually rise again once the buying pressure disappears.
Think of a Bond Like a Rental Property
Here’s another way to think about it.
Imagine a house produces exactly $50,000 a year in rent.
If you buy the property for $1 million, your rental yield is:
$50,000 ÷ $1,000,000 = 5%
If the property’s price rises to $1.25 million while the rent stays at $50,000:
Yield = 4%
If the property falls to $800,000:
Yield = 6.25%
The income didn’t change.
The price changed, and therefore the yield changed.
Bonds work in much the same way.
One Important Technical Detail
The examples above use current yield, which makes the concept easy to understand.
Professional bond investors usually focus more on yield to maturity (YTM).
Yield to maturity considers not only the interest payments but also whether the investor buys the bond above or below its face value and eventually receives the face value when the bond matures.
The calculation is more complicated, but the fundamental rule remains exactly the same:
Bond prices and bond yields move in opposite directions.
Once you understand that relationship, many seemingly complicated subjects—Treasury yields, Federal Reserve policy, mortgage rates, bond-market interventions, and even stock valuations—become much easier to understand.
