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学ぶ / Bonds & Rates / Foundations

Why Bond Prices and Yields Move Opposite

6 分で読めます 更新日 Aug 10, 2026

Bond prices and yields move in opposite directions because a bond pays a fixed coupon — when new bonds are issued at higher interest rates, older bonds paying less become less attractive, so their prices fall until their effective return matches the market. When rates fall, the opposite happens: older bonds paying more become more attractive, pushing their prices up. This inverse relationship is the single most important mechanic in the bond market.

The Core Idea: Fixed Payment, Moving World

A bond is essentially a loan you make to a government or company. In return, the borrower promises to pay you a fixed amount of interest — called the coupon — at regular intervals, then return your original sum (the face value, typically $1,000 per bond) when the bond matures. That word "fixed" is the key to everything on this page.

The world around that fixed payment keeps changing. Interest rates rise, fall, and shift with economic conditions. But the bond's coupon stays exactly as written. That tension — a frozen payment in a moving market — is why bond prices and yields are locked in a perpetual seesaw.

If you are new to how bonds work at a basic level, the Bond Market: The Complete Guide is a good place to start before diving into the mechanics here.

What "Yield" Actually Means

The word "yield" gets used loosely, so it is worth being precise. The coupon rate is simply the annual interest payment divided by the bond's face value — it is printed on the bond and never changes. Suppose a bond has a face value of $1,000 and pays $40 a year; its coupon rate is 4%. That number is fixed forever.

Yield to maturity (YTM) is something different. It is the total annualized return an investor would earn by buying the bond at its current market price and holding it all the way to maturity — accounting for the coupon payments and any difference between what they paid and what they get back at the end. YTM is what moves up and down as the bond's price changes in the market.

When people say "the yield on the 10-year Treasury rose today," they almost always mean yield to maturity, not the coupon rate. The coupon rate on that bond did not change. Its price did — and that is what caused the yield to move.

The Seesaw, Explained Step by Step

Here is the cleanest way to see why prices and yields move in opposite directions. Imagine the market is currently offering 4% on new bonds. You own an older bond that also pays 4% on its $1,000 face value — so $40 a year. At $1,000, your bond and a new bond are equally attractive. No problem.

Now suppose interest rates rise and new bonds start paying 5% — $50 a year on a $1,000 face value. Your old bond still only pays $40. Nobody will pay you $1,000 for a bond that earns $40 when they can get $50 elsewhere for the same price. To sell your bond, you have to lower the price until a buyer's effective return equals the going market rate of 5%. Price fell; yield rose.

The reverse is equally true. If rates fall to 3%, new bonds only pay $30 a year. Your bond, still paying $40, looks far more attractive. Buyers will compete to own it and bid its price above $1,000. Price rose; yield fell.

The seesaw always balances: the market adjusts the price of existing bonds until their yield to maturity matches whatever new bonds are offering.

Illustrative Arithmetic: Walking Through a Real Example

The following numbers are entirely hypothetical and labeled as an example. They are chosen to make the arithmetic clean, not to reflect any current or historical market level.

Suppose you buy a bond with these terms:

  • Face value: $1,000
  • Annual coupon: $40 (coupon rate: 4%)
  • Time to maturity: 1 year (keeping the math simple)

At maturity, you will receive $40 in interest plus $1,000 back — a total of $1,040. If you paid $1,000 for it, your yield to maturity is 4%. That matches the coupon rate because you bought it at face value.

Now suppose rates jump to 5% the day after you buy it, and you want to sell. A buyer can now get a brand-new 1-year bond paying $50 on a $1,000 investment. To make your bond equally attractive, you need to price it so the buyer still earns 5% on whatever they pay.

The buyer will receive exactly $1,040 at maturity no matter what — the coupon and face value are contractually fixed. Working backwards: if $1,040 represents a 5% return, then the price they should pay is $1,040 ÷ 1.05 ≈ $990.48. Your bond's price fell from $1,000 to roughly $990 because rates moved up by 1 percentage point.

Flip it around. If rates fell to 3%, a buyer would pay $1,040 ÷ 1.03 ≈ $1,009.71. The price rose above face value — called trading at a premium — because the fixed coupon now exceeds what the market offers on new debt.

Market Rate Bond Price (illustrative) Relationship to Face Value Yield to Maturity
3% ~$1,009.71 Premium (above $1,000) 3%
4% $1,000.00 Par (at face value) 4%
5% ~$990.48 Discount (below $1,000) 5%

Notice that in every row, the yield to maturity equals the market rate. The price moved to make that happen automatically — that is the market doing its job.

Duration: Why Some Bonds Move More Than Others

Not all bonds react to the same rate change with the same price swing. A bond maturing in 30 years has far more future payments affected by a rate change than one maturing in 1 year. The concept that measures this sensitivity is called duration — specifically, how much a bond's price changes for each 1 percentage-point move in yields.

Longer-maturity bonds have higher duration and therefore larger price swings for the same yield move. Shorter-maturity bonds are less sensitive. This is why traders and economists pay close attention to duration when assessing how a bond portfolio might respond to changes in interest rates.

The 10-year government bond yield is watched so closely precisely because it sits at a meaningful point on this spectrum — long enough to be sensitive to expectations, short enough to trade actively. You can track live government bond yields across dozens of countries on the bonds page.

Why This Matters Beyond the Bond Market

The price-yield relationship sends ripples across every asset class, which is why understanding it matters even if bonds are not your primary focus.

When bond yields rise, the return available from a "safe" government bond increases. That raises the bar for riskier assets like stocks — investors comparing a 5% government yield to a company's earnings yield will demand more from equities, which can pressure valuations. Historically, sharp moves in bond yields have coincided with significant moves in equity markets.

Rising yields also strengthen a country's currency in foreign-exchange markets, because higher yields attract capital from abroad. Falling yields tend to weaken it. The factors that move exchange rates are deeply tied to relative bond yields across countries.

Gold, which pays no coupon at all, is often discussed in terms of real yields — bond yields adjusted for inflation. When real yields fall, the opportunity cost of holding gold (which earns nothing) decreases, and gold historically tends to attract more attention. You can explore that dynamic further in the gold guide.

Reading Yield Changes in Practice

On a market data page, bond yields are quoted in percentage terms — for example, "4.25%." When a site shows the yield changed by "+0.05," that means five basis points (one basis point equals one-hundredth of a percentage point, or 0.01%). Bond markets use basis points because the moves that matter are often small in percentage terms but large in dollar value across huge portfolios.

A percent-change column for a bond's price tells you how much the bond's traded value moved. A percent-change column for its yield tells you how the market's rate expectation shifted. Both columns describe the same event from opposite ends of the seesaw. For a deeper look at how to read these columns across any asset, see Day, Week, YTD, YoY: Reading Percentage Moves.

Economists also watch the shape formed by yields across many maturities at once — from 3-month bills to 30-year bonds. That shape is called the yield curve, and its slope carries its own signals about where markets expect interest rates and the economy to head. The yield curve guide covers that in full.

よくある質問

Why do bond prices fall when interest rates go up?
A bond pays a fixed coupon that was set when it was issued. When new bonds come to market paying higher rates, older lower-paying bonds become less attractive, so their prices drop until the effective return — the yield to maturity — matches what new bonds are offering. The price adjusts because the coupon cannot.
What is the difference between a bond's coupon rate and its yield?
The coupon rate is fixed at issuance and is simply the annual interest payment divided by face value — it never changes. Yield to maturity is a calculated figure that reflects the bond's current market price; it rises when the price falls and falls when the price rises, always adjusting to reflect what a buyer would actually earn by holding the bond to maturity.
What does it mean when a bond trades at a "discount" or a "premium"?
A bond trades at a discount when its market price is below its face value, which happens when market interest rates are higher than the bond's coupon rate. It trades at a premium when its price is above face value, which happens when market rates have fallen below the coupon rate and the bond's fixed payments look attractive compared to what new bonds offer.
Do all bonds react the same way to interest-rate changes?
No — the size of a bond's price move depends on its duration, which is largely driven by how long until it matures. A 30-year bond has many more future payments exposed to a rate change than a 1-year bond, so its price swings much more for the same shift in yields. This sensitivity is measured and compared using a concept called duration.
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