Bonds are loans. When you buy a bond, you are lending money to a government, municipality, or corporation. In exchange, the borrower pays you interest (called the coupon) over a set period and returns your principal when the bond matures. Bonds are considered lower-risk than stocks because bondholders are paid before equity shareholders if a company fails — but they also deliver lower long-term returns.
Most investors should hold some bonds, but how much and which type depends on your goals and time horizon.
Why Invest in Bonds
Bonds serve two main purposes in a portfolio:
- Income: Bonds pay regular interest, making them useful for investors who need cash flow — especially retirees.
- Diversification and stability: Bonds often move in the opposite direction of stocks during market downturns. A portfolio with both stocks and bonds typically experiences less volatility than one made entirely of equities.
The classic “60/40 portfolio” — 60% stocks, 40% bonds — is built on this relationship. While the diversification benefit has been less reliable during periods when stocks and bonds fall together (as in 2022), bonds remain a fundamental tool for risk management.
Types of Bonds
U.S. Treasury Bonds
Issued by the federal government. Considered the safest bonds available since they are backed by the U.S. government. Treasury bills (T-bills) mature in under a year; Treasury notes mature in 2–10 years; Treasury bonds mature in 20–30 years. Interest is exempt from state and local taxes.
Municipal Bonds (Munis)
Issued by state and local governments to fund infrastructure, schools, and public projects. Interest is typically exempt from federal income tax and often exempt from state taxes in the issuing state. Most useful for investors in high tax brackets — the tax advantage increases the effective yield relative to comparable taxable bonds.
Corporate Bonds
Issued by companies to raise capital. Higher yields than Treasuries because corporations carry more credit risk. Rated by agencies like Moody’s and S&P — investment-grade bonds (BBB/Baa or above) are considered relatively safe; high-yield or “junk” bonds (below BBB/Baa) offer higher yields in exchange for higher default risk.
I Bonds and TIPS
Treasury bonds linked to inflation. I bonds are purchased directly from TreasuryDirect.gov; TIPS trade on the secondary market. Both protect purchasing power during inflationary periods.
The Relationship Between Bond Prices and Interest Rates
This is the most important concept for bond investors to understand: bond prices move inversely to interest rates.
When interest rates rise, existing bond prices fall. When rates fall, bond prices rise. Here is why: if you hold a bond paying 3% and new bonds are issued at 5%, your 3% bond is less attractive — so its market price drops until its effective yield matches the new market rate.
This relationship is amplified by duration. Long-term bonds are more sensitive to rate changes than short-term bonds. In 2022, long-term Treasury bond funds lost 20–30% as rates rose sharply — a reminder that “safe” bonds can still lose significant value in rising-rate environments.
How to Invest in Bonds
Bond ETFs and Mutual Funds
For most investors, the simplest approach is buying bond ETFs or mutual funds through a brokerage or retirement account. These funds hold diversified portfolios of bonds and trade like stocks.
Popular options:
- BND (Vanguard Total Bond Market ETF): Broad exposure to U.S. investment-grade bonds. Expense ratio 0.03%.
- AGG (iShares Core U.S. Aggregate Bond ETF): Similar broad exposure. Expense ratio 0.03%.
- VGSH / SHY: Short-term Treasury ETFs for lower interest-rate sensitivity.
- VTIP / SCHP: TIPS ETFs for inflation protection.
- MUB (iShares National Muni Bond ETF): Municipal bonds for tax-exempt income.
Buying Individual Bonds
You can purchase individual Treasury bonds directly from TreasuryDirect.gov with no fees. For corporate and municipal bonds, you buy through a brokerage — note that the bid-ask spreads on individual bonds can be wide, especially for smaller purchases.
Building a “bond ladder” — purchasing individual bonds with staggered maturities (e.g., 1-year, 2-year, 3-year, 4-year, 5-year) — provides predictable cash flows and reduces reinvestment risk. As each bond matures, you reinvest at the current rate.
Treasury Direct for U.S. Treasuries and I Bonds
For direct Treasury purchases without brokerage fees, use TreasuryDirect.gov. You can buy T-bills, notes, bonds, and I bonds here. I bonds in particular can only be purchased through TreasuryDirect (electronic) or via your tax refund (paper).
Bonds in a Retirement Account vs. Taxable Account
Tax efficiency matters for bond placement:
- Taxable brokerage account: Municipal bonds are often more efficient here because their tax-exempt interest is most valuable to investors who would otherwise owe tax on it. TIPS can be tax-inefficient in taxable accounts because you owe tax on inflation adjustments even before you receive them.
- Tax-advantaged accounts (IRA, 401(k)): Taxable bonds (Treasuries, corporate bonds) are often better held here, where the interest income is sheltered from annual taxes.
How Much of Your Portfolio Should Be Bonds
A simple rule of thumb: subtract your age from 110 to get your stock allocation; the remainder goes to bonds. A 40-year-old would hold 70% stocks and 30% bonds by this formula.
More precise guidance depends on your risk tolerance, time horizon, and income needs. Target-date retirement funds automatically shift toward higher bond allocations as the target date approaches — a useful default if you do not want to manage the allocation manually.
The Bottom Line
Bonds provide income, reduce portfolio volatility, and offer diversification from equities. For most individual investors, bond ETFs are the simplest and most cost-effective way to access them. The key risk to understand is interest-rate sensitivity: longer-duration bonds lose more value when rates rise. Match your bond duration to your time horizon, and hold bonds primarily in tax-advantaged accounts when possible.