How Bonds Work: Everything You Need To Know

How Bonds Work: Everything You Need To Know

Understanding how bonds work, from the types and risks to how yields get set, shows why owning them is about far more than the daily price change.

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Every few years, the financial media decides that bonds are “broken.” The headline usually follows a stretch where bond prices fell alongside stocks, and the conclusion is always the same: why own something that loses money when it is supposed to be “safe”?

Here’s the problem with that argument. It judges a bond by the one number that matters least to its owner. Understanding how bonds work starts with a simple idea that most investors have never been taught. The price on your statement is a running estimate of what someone else would pay you today. It is NOT the amount the issuer has promised to pay you.

While that distinction may sound academic, wait until you watch what it does to investor behavior. For years, bond fund prices only went higher. However, the last 5 years have caused some pain for individuals, and with bond funds down 12%, their first inclination is to sell.

Of course, this is usually the point where investors sell near the low, then swear off bonds for a decade. People who understand the contract they own tend to do the opposite. This article is the long version of that conversation: what bonds are, the types you’ll run into, the risks that actually matter, how yields get set, and why the job bonds do in a portfolio has very little to do with the daily print.

How Bonds Work: A Contract, Not A Stock Quote

It’s hard to understand how bonds work, when no one really explains them. Once you strip away the jargon, a bond is just a loan you make to a government or a company. That’s it. Nothing more. The borrower agrees in writing to pay a fixed interest rate (the coupon) on a set schedule. It also agrees to return your principal, the par or face value, on a specific date called the maturity.

That’s the whole deal. A simple contract.

Everything else you’ll hear about bonds, from duration and convexity to spreads and the yield curve, is a way of describing what happens to the value of that promise between the day you buy it and the day it ends. A 10-year Treasury with a 4% coupon pays $40 a year per $1,000 bond, in two $20 installments. At the end of year ten, it hands back the $1,000.

A stock makes none of those promises. There is no maturity date, no contractual payment, and no guarantee you ever get your money back. This is why the two assets behave so differently over time, even when they move together for a few weeks. With a stock, the market price is the only exit. With a bond held to maturity, the market price is one of two exits. The other is written into the contract.

Think of it like owning a rental house with a signed ten-year lease. If rents in the neighborhood jump, the market value of your house (with its below-market lease attached) falls, because a buyer would rather collect today’s higher rents. Your tenant, however, keeps paying exactly what the lease says. When the lease ends, you get the house back and can rent it at the going rate. A bond’s market price is the appraisal of the lease, not the lease itself. Investors who confuse the two make most of the mistakes that cost them money in fixed income.

contract vs quote

The Seesaw Between Price And Yield

Let’s start with the inverse relationship between bond price and the yield. When a bond is issued, its coupon is fixed for life. The only thing that changes is the yield that new buyers demand. Let me explain.

Let’s assume you have a bond with a 4% interest rate. However, the current going interest rate on a new bond of similar credit quality and duration is 5%. If you try to sell your 4% coupon bond today, the bond’s price must decline so that the “yield to maturity” equals 5%. In other words, the buyer of your 4% bond will pay less than face value of the bond today, so that when it matures at “par” in the future, the combined return of the coupon payments and the capital gain in the bond equates to a 5% rate of return.

Of course, when rates fall, the reverse happens: your older, higher-coupon bond becomes worth more than par. That inverse relationship is the seesaw every bond investor rides.

The number that captures this is the yield to maturity. It’s the annualized return you lock in by buying at today’s price and holding to the end. That assumes you collect every coupon, reinvest each one at the same rate, and get par back. In other words, the yield to maturity is the market’s price tag stated as a return. That’s why bond traders quote yields instead of prices.

How far the price moves depends mostly on time. A bond that matures in two years doesn’t have much room to be “wrong” about rates. A 30-year bond does. The measure of that sensitivity is “duration,” which is roughly the percentage price change for a one-point move in yields. The chart below shows the math for a 4% Treasury when its yield rises from 4% to 5%.

one point

Notice the zero-coupon bond on the far right. It pays nothing until maturity, so all of its value sits at the end of the timeline. Every change in rates hits it with full force. That’s the instrument behind most of the dramatic “bonds crashed” headlines. The same math explains why the market treats something like a 100-year corporate bond as a bet on rates as much as on the issuer. Long duration is a volatility choice. It isn’t a statement about whether you’ll be paid.

See more: Why Advisors Are Using High-Yield ETFs