What Is a Bond and How Bond Yields Work

Bonds as Loans

When a government or corporation needs to raise money, it has two main options: issue stock (equity) or issue bonds (debt). A bond is essentially a loan you make to the issuer. In exchange for lending your money, the issuer promises to pay you regular interest — called the coupon — and to return your principal in full when the bond reaches its maturity date.

Bonds are a fundamental component of most investment portfolios. They tend to be less volatile than stocks, generate predictable income, and often — though not always — rise in value when stocks fall, providing a diversification benefit. Understanding how bond pricing and yields actually work is essential to using them wisely.

Key Bond Terminology

Before going further, a few terms are critical to understand:

• Face value (par value): The amount returned to the bondholder at maturity. Most bonds have a $1,000 face value.
• Coupon rate: The annual interest payment expressed as a percentage of face value. A $1,000 bond with a 5 percent coupon pays $50 per year, typically in semi-annual installments of $25.
• Maturity: The date on which the issuer repays the face value. Bonds can mature in months or decades.
• Yield: The actual return an investor earns, accounting for the price paid for the bond. Yield and price move in opposite directions.
• Duration: A measure of a bond's sensitivity to interest rate changes, expressed in years.

Why Bond Prices and Yields Move in Opposite Directions

This inverse relationship is the concept that confuses most new bond investors. Here is the intuition: imagine you hold a bond paying 3 percent coupon on a $1,000 face value — $30 per year. Then interest rates in the broader market rise to 5 percent. A newly issued bond now pays $50 per year on the same face value. Your older bond looks less attractive. To sell it, you must lower the price until a buyer's effective return equals the current market rate of 5 percent.

The reverse is equally true. If rates fall from 3 to 1 percent, your existing bond paying 3 percent becomes very attractive. Buyers will bid up its price until the effective yield falls to match the lower prevailing rate. When rates fall, existing bond prices rise. When rates rise, existing bond prices fall.

Understanding Yield to Maturity

Yield to maturity (YTM) is the most complete measure of a bond's return. It represents the total annualized return you would earn if you bought the bond at its current price and held it all the way to maturity, reinvesting all coupon payments at the same rate. YTM accounts for the discount or premium you paid versus face value, all coupon payments, and the return of principal at maturity.

When comparing bonds, YTM is the right metric to use rather than the coupon rate. Two bonds with the same coupon rate but different prices will have very different yields to maturity.

Types of Bonds

• U.S. Treasury bonds: Issued by the federal government and backed by the full faith and credit of the United States. Considered the safest bonds in the world. Treasury bills (T-bills) mature in under a year; Treasury notes in two to ten years; Treasury bonds in twenty to thirty years. Treasury Inflation-Protected Securities (TIPS) adjust the principal with inflation.
• Municipal bonds (munis): Issued by state and local governments. Interest is generally exempt from federal income tax and often state tax for residents. The tax advantage makes them particularly valuable for investors in high tax brackets.
• Corporate bonds: Issued by companies. They pay higher yields than Treasuries to compensate for default risk. Investment-grade bonds (BBB/Baa and above) have relatively low default risk. High-yield bonds (also called junk bonds) are rated below investment grade and carry significantly higher default risk alongside higher yields.
• Agency bonds: Issued by government-sponsored enterprises like Fannie Mae and Freddie Mac. Slightly higher yield than Treasuries with implied government backing.

Duration: Measuring Interest Rate Sensitivity

Duration measures how much a bond's price will change in response to a one-percentage-point change in interest rates. A bond with a duration of 7 years will rise approximately 7 percent in price if rates fall by 1 percent, and fall approximately 7 percent if rates rise by 1 percent.

Longer-maturity bonds have higher duration — more future cash flows are vulnerable to discount rate changes. Short-duration bonds (under three years) are much less sensitive to rate movements. In environments where interest rates are expected to rise, shorter-duration bonds offer less price risk. When rates are expected to fall, longer-duration bonds offer more price appreciation potential.

The Yield Curve and What It Signals

The yield curve plots the yields of Treasury bonds across different maturities — from three months to thirty years. In normal economic conditions, the yield curve slopes upward: investors demand higher yields for lending money longer-term due to time risk and inflation uncertainty.

An inverted yield curve — when short-term yields exceed long-term yields — has historically preceded recessions. When investors expect economic weakness, they flock to long-term bonds, bidding up prices and pushing yields down, while the Federal Reserve holds short-term rates elevated to fight inflation. Monitoring the yield curve is a key practice for understanding economic expectations, though it is not a perfect predictor.

Bonds in a Portfolio

Bonds typically provide stability and income in a diversified portfolio. The classic 60/40 portfolio — 60 percent stocks, 40 percent bonds — has been a long-standing benchmark for balanced investors. However, the optimal bond allocation depends on your age, time horizon, income needs, and risk tolerance.

For investors who need current income, shorter-duration, higher-quality bonds and bond funds provide predictable cash flow with manageable risk. For long-term investors primarily concerned with growth, bonds serve mainly as a volatility buffer — reducing portfolio swings without significantly dragging on total return. As interest rates rose sharply after 2022, bonds endured unusual losses, reminding investors that even conservative assets carry risk when rate movements are dramatic.