Bonds Demystified: Yield, Duration, and Credit Risk in Plain Language

What a bond actually is

A bond is a loan. When you buy a bond, you lend money to a government, municipality, or corporation. The borrower promises to pay you a fixed rate of interest at regular intervals and return your principal on a set date called the maturity date. That fixed payment stream is why bonds are called fixed-income securities.

Bonds occupy a different role than stocks in a portfolio. Stocks represent ownership in a company; bonds represent a debt claim. Because bondholders are creditors rather than owners, they generally have a higher priority than stockholders if an issuer runs into financial trouble. See how stocks, bonds, and funds each function in a portfolio for a fuller comparison.

The three concepts that matter most when evaluating any bond are yield, duration, and credit risk. Each one answers a distinct question: How much will this bond pay me? How sensitive is its price to interest rate changes? How likely is the borrower to repay?

Yield: what you actually earn

A bond's stated interest rate is its coupon rate, expressed as a percentage of face value. A $1,000 bond with a 4% coupon pays $40 per year. But the coupon rate is not the same as yield.

Yield reflects what you actually earn based on the price you pay. Bond prices move in the secondary market after issuance. If you pay $950 for a $1,000 bond with a $40 annual coupon, your yield is higher than 4% because you are earning $40 on a smaller investment, and you will also receive the full $1,000 at maturity. If you pay $1,050, your yield is lower. This inverse relationship, bond prices fall when yields rise and vice versa, is one of the most important mechanics in fixed-income investing.

Yield to maturity (YTM) is the most complete measure. It accounts for coupon payments, any difference between purchase price and face value, and the time remaining until maturity. When investors or financial media quote a bond's yield, they usually mean YTM. For a plain-language definition of YTM alongside other investing terms, the key investing terms reference glossary is a useful starting point.

Duration: measuring interest rate sensitivity

Duration measures how much a bond's price is expected to change when interest rates move. It is expressed in years, but it functions as a sensitivity gauge. A bond with a duration of 7 years will lose roughly 7% of its market value if interest rates rise by 1 percentage point, and gain roughly 7% if rates fall by 1 point.

Duration depends on maturity, coupon rate, and yield. Longer maturities produce higher duration. Lower coupon rates produce higher duration because more of the bond's total cash flow arrives at maturity rather than in earlier coupon payments. A zero-coupon bond, which pays no coupons and returns all value at maturity, has a duration equal to its maturity.

For retirement savers, duration matters in portfolio construction. Short-duration bonds carry less interest rate risk but typically offer lower yields. Long-duration bonds offer higher yields in normal market conditions but are more vulnerable to price drops when rates rise. Holding bonds closer to maturity reduces this risk because price fluctuations converge toward face value as the maturity date approaches.

Credit risk: the borrower's ability to repay

Credit risk is the possibility that the bond issuer will miss an interest payment or fail to return principal. Independent rating agencies such as Moody's, S&P Global, and Fitch assess issuers and assign letter grades. Investment-grade bonds, typically rated BBB/Baa or above, carry lower default risk. Bonds rated below that threshold are called high-yield or speculative-grade bonds and carry meaningfully higher risk.

U.S. Treasury bonds are backed by the federal government and carry the lowest credit risk available in the U.S. market. Corporate bonds and municipal bonds carry varying levels of credit risk depending on the issuer's financial position. Investors in lower-rated bonds receive a higher yield as compensation for accepting greater risk. That additional yield above a comparable Treasury is called the credit spread.

Credit ratings are not permanent. An issuer's financial condition can improve or deteriorate, and rating agencies revise their assessments accordingly. A bond rated investment-grade when purchased can be downgraded, which typically causes its price to fall. Diversifying across multiple issuers and sectors limits the impact of any single default or downgrade on a portfolio.

This article is for informational purposes only and does not constitute personalized financial, investment, tax, or legal advice. Bond investing involves risk, including the possible loss of principal. Consult a qualified financial adviser before making decisions about your own portfolio.