AP Syllabus focus: ‘Previously issued bond prices move inversely with interest rates, and holding money means giving up potential interest earnings.’
Bond markets connect interest rates to asset values. Understanding why existing bond prices move opposite market rates, and why holding money has an opportunity cost, clarifies household portfolio choices and monetary policy transmission.
Bond prices and interest rates: the inverse relationship
Key idea: old bonds must compete with new rates
A bond is a financial asset that promises specified payments (coupons and/or principal).
When the market interest rate rises, newly issued bonds offer higher returns, so previously issued bonds become less attractive unless their price falls. When market interest rates fall, older bonds with higher promised payments become more attractive, so their price rises.
Interest rate up → bond price down
Interest rate down → bond price up
This is an asset-market adjustment: investors can switch between bonds, money, and other assets, so prices change until returns are comparable for similar risk.
Present value intuition
A bond’s price reflects the present value of its promised future payments, discounted at the prevailing market interest rate. A higher discount rate reduces present value, lowering the bond price.
= Current bond price in dollars
= Market interest rate per period (decimal)
= Coupon payment per period in dollars
= Face (par) value repaid at maturity in dollars
= Number of periods until maturity
Even without calculating, AP Macroeconomics expects you to use this logic: as i increases, the discounted value of each future payment falls, so P falls.
Why “previously issued” matters
Newly issued bonds typically set coupons so that their price is near par (face value). Older bonds have fixed coupons set in the past, so the only way they can offer a competitive return today is through a change in price in the secondary market.
If an older bond’s coupon is low relative to current rates, it must sell at a discount (below par).
If an older bond’s coupon is high relative to current rates, it can sell at a premium (above par).
The opportunity cost of holding money
Money yields liquidity, not (much) interest
Money (especially currency and many checkable deposits) is highly liquid and useful for transactions, but it usually pays little or no interest. Choosing to hold more money means holding fewer interest-bearing assets like bonds.
Opportunity cost of holding money: the interest income (or higher return) forgone by holding wealth in money balances instead of interest-bearing assets.
This opportunity cost is closely tied to the nominal interest rate: when nominal rates rise, the foregone interest from holding money increases.
This money market diagram shows money demand sloping downward with respect to the nominal interest rate because the interest rate is the opportunity cost of holding money. With money supply drawn as a vertical line, equilibrium occurs where money demand intersects money supply, determining the equilibrium interest rate and quantity of money held. Source
Link to behavior and markets
Because of this trade-off, higher interest rates tend to reduce desired money holdings and increase willingness to hold bonds.
When interest rates rise:
Opportunity cost of money rises
People try to reduce money balances
Demand shifts toward interest-bearing assets
When interest rates fall:
Opportunity cost of money falls
People are more willing to hold money for liquidity and convenience
What you should be able to do on AP-style prompts
Explain movements using clear cause-and-effect
Be ready to state the chain in words (no computation required):
“Market interest rates rise” → “new bonds offer higher returns” → “existing bond prices fall to raise their effective return”
“Holding money” → “gives liquidity” but → “forgoes potential interest earnings on bonds”
Use precise vocabulary
Use these high-utility phrases accurately:
secondary market, discount/premium, present value, discount rate, nominal interest rate, foregone interest earnings
FAQ
More payments arrive further in the future, so a rate change affects more heavily discounted cash flows.
Small changes in rates therefore cause bigger swings in present value for long maturities.
They make a single payment at maturity, so price is pure discounting of one future amount.
With no coupons, all value is sensitive to the discount rate applied to that final payment.
Coupon rate is fixed by the bond’s terms, based on face value.
Yield reflects the return given the bond’s current market price; when price changes, yield changes.
Money provides transaction convenience, certainty of nominal value, and immediate liquidity.
Some households and firms must hold money to pay bills even when the foregone interest is high.
Yes. If default risk perceptions change, required returns can change independently of policy rates.
A higher required return from risk can push prices down even without a change in the general interest rate.
Practice Questions
(2 marks) Explain why the price of a previously issued bond falls when market interest rates rise.
States inverse relationship: interest rates up → existing bond prices down (1)
Explains competition/present value/return adjustment logic (1)
(6 marks) A central bank policy change causes market interest rates to rise.
(a) Explain how and why this affects prices of previously issued bonds. (3 marks)
(b) Explain what happens to the opportunity cost of holding money and how this changes people’s preferred asset holdings between money and bonds. (3 marks)
(a)
Identifies that previously issued bond coupons are fixed, so adjustment occurs via price (1)
Explains higher market rate increases discounting or makes new bonds more attractive (1)
Concludes existing bond prices fall to offer competitive return (1)
(b)
Defines/opines opportunity cost rises: more interest forgone by holding money (1)
Predicts reduced desired money balances (1)
Predicts increased preference for bonds/interest-bearing assets (1)
