Bond Prices and Market Interest Rates Move in Opposite Directions

What this means

When a corporation or a government needs to borrow, one option is to issue a bondA debt security in which the issuer borrows money from the buyer and promises fixed interest payments plus repayment of the face value on a stated date.. The buyer hands over money now. In exchange, the issuer promises a fixed stream of interest payments and repayment of the face valueThe amount the bond issuer repays at maturity, also called par value. Coupon payments are calculated as a percentage of this amount. on the maturityThe date on which the issuer repays the bond's face value and the bond ceases to exist. date.

Here is the part that surprises people. You are not required to hold the bond until maturity. Bonds are traded, and the market where already-issued bonds change hands is called the secondary marketThe market in which previously issued securities are resold among investors rather than sold by the original issuer.. If you sell early, nobody guarantees you the face value. You get whatever a buyer is willing to pay, which is determined by supply and demand in the bond market on that day.

So what determines what a buyer will pay? The critical fact is that the coupon paymentThe fixed dollar interest payment a bond makes, set when the bond is issued and unchanged thereafter. is locked in dollars at issue. It cannot adjust. But the interest rates available on brand new bonds change constantly. A buyer choosing between your old bond and a new one will not overpay for the worse deal or underpay for the better one. The only variable that can move is the price of your bond.

Work through the case the standard poses. You hold a bond with a face value of 1,000 dollars paying a fixed 5 percent, so it pays 50 dollars a year. Now market interest rates fall to 4 percent. New 1,000 dollar bonds pay only 40 dollars a year. Your bond pays 50 dollars a year, and that stream is contractually fixed. Every investor in the market would rather have 50 dollars a year than 40 dollars a year for the same 1,000 dollars. Demand for your bond rises, and buyers bid its price above 1,000 dollars. They keep bidding until the 50 dollars a year, measured against the higher price paid, produces roughly the same 4 percent return as everything else. That is the yieldThe return an investor actually earns on a bond, calculated from its coupon payments relative to the price actually paid for it., and it is the yield, not the coupon, that the market equalizes.

Run it backward and the logic holds. If market rates rise from 5 percent to 6 percent, new bonds pay 60 dollars a year while yours still pays 50. Nobody pays full price for the inferior stream, so your bond's price falls below 1,000 dollars until its yield is competitive. This is the inverse relationship: rates up, prices down; rates down, prices up. It is not a market mood. It is arithmetic forced by a fixed payment meeting a changing benchmark.

Why it matters

The phrase "bonds are the safe investment" hides a real risk. A bond held to maturity does return its face value, assuming the issuer does not default. But a bond sold early can absolutely lose money, and the loss has nothing to do with the issuer's health. A perfectly sound government bond can be worth less than you paid simply because rates rose after you bought it. This is interest rate riskThe risk that a bond's market price will fall because market interest rates have risen since the bond was purchased., and it is the reason retirement funds and college savings plans shift their bond holdings as a target date approaches.

It also explains a headline pattern you will see for the rest of your life. When a central bank signals higher rates, financial news reports that bond markets fell. Those are not two separate events. They are the same event described twice.

Try it

1. Set up the base case on paper. A bond has a face value of 1,000 dollars, a fixed coupon rate of 5 percent, and pays annually. Write down the exact dollar coupon payment. Confirm that if you buy it at face value, your yield equals the coupon rate.
2. Drop the market rate to 4 percent. A competing new 1,000 dollar bond now pays how many dollars per year? Write both dollar figures side by side and state plainly which stream an investor prefers.
3. Estimate the new price. Ask: what price P would make a fixed 50 dollar annual payment yield about 4 percent? Solve 50 divided by P equals 0.04. Note whether your answer is above or below 1,000 dollars, and explain in one sentence why that direction was inevitable before you did any arithmetic.
4. Now reverse it. Market rates rise from 5 percent to 6 percent. Repeat step 3 using 0.06. Explain why a buyer refuses to pay 1,000 dollars for your bond now, and what specifically they are being compensated for by the discount.
5. Build a small table with market rates of 3, 4, 5, 6, and 7 percent in one column and your estimated bond price in the next. Plot price against market rate. Describe the shape and slope of what you drew in one sentence.
6. Get real data. Open FRED, the Federal Reserve Bank of St. Louis data site, and pull a long series for the 10-year Treasury constant maturity yield. Pick any two dates several years apart where the yield clearly moved, and record both values. Do not use a number you remember; look it up.
7. Using your two real yields, state which direction the price of an existing bond issued before the first date would have moved between those dates, and by roughly what proportion. Explain your reasoning without hedging.
8. Write a short response to this claim: "I bought a government bond, so I cannot lose money." Identify precisely what is true in the claim and what is false, and name the condition under which each holds.
9. Extend it. Two bonds pay the same coupon rate, but one matures in 2 years and the other in 20 years. Argue which one's price swings more when market rates move, and justify your answer by pointing to how many fixed payments are locked in at the wrong rate.

Check yourself