Bonds & Bond ETFs

Definition

A bond is a loan. When you buy a bond, you are lending money to the issuer — a government, a city, or a company — and in return the issuer promises two things: to pay you interest on a set schedule, and to give your original money back on a specific future date. That is the whole deal, and four terms describe it:

• Par (or face) value — the amount the issuer will repay at the end, almost always

$1,000 per bond. This is the loan's principal.

• Coupon — the fixed interest rate the bond pays, quoted as a percentage of par. A 5%

coupon on a $1,000 bond pays $50 a year, usually split into two $25 payments.

• Maturity — the date the loan comes due and the issuer returns your par value. Bonds

range from a few months to 30 years.

• Yield — what you actually earn, which depends on the *price you paid*, not just the

coupon. This is the number that moves.

The crucial idea is that a bond's coupon is fixed for life, but its price trades up and down in the market after it is issued. When the price changes, the yield changes with it — in the opposite direction. This inverse price-yield relationship is the single most important thing to understand about bonds, and everything else builds on it.

A bond ETF is a fund that holds hundreds or thousands of individual bonds in one tradeable package. Funds like BND and AGG each own thousands of U.S. bonds and trade on an exchange like a stock. Instead of picking single bonds yourself, you buy one share and own a slice of the whole basket, collecting the pooled interest as a monthly distribution.

Why It Matters

For an income investor, bonds do two jobs that stocks and dividend ETFs alone cannot.

The first is steady income. A bond's coupon is contractual — the issuer owes it regardless of how the stock market is doing. That makes bond income more predictable than a dividend, which a company can cut at any time. A bond ETF passes this pooled interest through to you, typically once a month.

The second is diversification. High-quality bonds — especially U.S. Treasuries — often hold their value or rise when stocks fall, because nervous investors move money into safety. Adding bonds to a stock-heavy portfolio can soften the deepest drops and smooth the ride, which matters most for retirees drawing income who cannot afford to sell stocks in a crash.

To use bonds well you have to understand the two risks that drive their price.

Interest-rate risk (duration). When market interest rates rise, newly issued bonds pay more, so existing bonds with lower coupons become less attractive — and their prices fall until their yield matches the new going rate. When rates fall, the reverse happens and bond prices rise. Duration measures how sharply a bond or fund reacts. A short-term bond fund might have a duration of 2, meaning a 1% rate move changes its price by roughly 2%. A long-term fund like TLT, which holds 20-plus-year Treasuries, can have a duration near 17 — so the same 1% rate move swings its price about 17%. Long bonds are far more volatile than short bonds even when the borrower is identical.

Credit risk. This is the chance the issuer fails to pay you back. It is ranked by borrower quality:

• Treasuries are backed by the U.S. government and carry essentially no credit risk.

Their price moves come almost entirely from interest rates.

• Investment-grade corporates are bonds from financially solid companies. They pay a

bit more than Treasuries to compensate for a small default risk.

• High-yield ("junk") bonds come from weaker borrowers. They pay the highest coupons

but carry real risk of default, and they can fall alongside stocks in a downturn.

Key point: Treasury risk is mostly about interest rates; junk-bond risk is mostly about whether the borrower survives. A "bond fund" can mean very different things depending on what it holds.

Yield-To-Maturity vs Current Yield

Because a bond's price and coupon can differ, "yield" is measured two ways, and mixing them up leads to bad comparisons.

• Current yield is just the annual coupon divided by the price you paid. Buy a 5%

coupon ($50/year) bond for $900 and the current yield is about 5.6%. It ignores what happens at maturity.

• Yield-to-maturity (YTM) is the total annualized return if you hold the bond to the

end — it folds in the coupons *and* the gain or loss between your purchase price and the $1,000 par you receive at maturity. YTM is the more complete number and the one to compare across bonds.

Bought a bond for $900
  Coupon: $50 per year (5% of $1,000 par)
  Current yield = $50 / $900        = ~5.6%
  Yield-to-maturity also adds the
  +$100 gain back to par at the end = higher than 5.6%

For a bond *ETF*, you do not look up YTM on a single bond. Instead, funds quote a standardized 30-day SEC yield — a formula that annualizes the income the fund earned over the last 30 days, net of expenses, using SEC rules so every fund is measured the same way. When comparing BND, AGG, and other bond ETFs, the 30-day SEC yield is the apples-to-apples figure — not the trailing distribution, which can be distorted by timing.

Example

The figures below are illustrative and chosen to show the relationships — they are not live quotes. Real yields and durations move constantly, so look each fund up for current numbers. What matters is the *pattern*, not the exact percentages.

Read down the table and the trade-offs come into focus. Notice that moving from short to long Treasuries barely raises the yield but sharply raises the duration — you take on far more price volatility for a small income bump. That is why a long-bond fund like TLT can drop 15% or more in a year when rates rise, even though the U.S. government will always make its payments. The risk there is not default; it is interest rates.

Move down to corporates and high-yield and the yield climbs because you are now being paid for credit risk. A junk-bond fund's fat yield is compensation for the chance some borrowers default — and those funds tend to sink when the economy weakens, right when you might have hoped bonds would protect you.

A broad fund like BND or AGG blends most of these — mostly Treasuries and investment-grade corporates across many maturities — into one intermediate-duration, high-quality holding. That is why they are the default "core bond" position for most portfolios: middling yield, moderate rate sensitivity, very little default risk.

How a Bond ETF Differs From a Single Bond

Owning a bond ETF is not the same as owning one bond, and the differences change how you should think about it.

• No fixed maturity. A single bond has a maturity date when you get your exact par

value back. A bond ETF never matures — as bonds inside it come due, the manager buys new ones to keep the fund running. You are not guaranteed to get a specific dollar amount back on a specific day.

• The price (NAV) floats — and can lose value. A held-to-maturity bond returns par

regardless of interim price wiggles. A bond ETF's share price tracks its net asset value (NAV), which rises and falls daily with interest rates. If rates jump, the fund's NAV drops and stays down until either rates ease or its bonds gradually roll into higher-yielding ones. There is no maturity date that rescues the price.

• Constant income, not a lump sum. Instead of two coupon payments a year from one

bond, an ETF pays a blended distribution monthly from thousands of bonds paying on different schedules.

• Instant diversification and liquidity. One share of AGG

spreads your money across thousands of issuers, so a single default barely registers — and you can sell any second the market is open, unlike an individual bond that can be hard to trade.

The practical upshot: a bond ETF is simpler and more diversified, but you trade away the "I get exactly $1,000 back on this date" certainty of a single bond for a floating price.

Common Mistakes

• Thinking bond funds can't lose money. They can. When interest rates rose sharply in

2022, broad bond funds like BND fell over 10% — because their NAV floats and older, lower-coupon bonds repriced downward. "Bonds are safe" refers to *default* risk on Treasuries, not to a guarantee against price drops.

• Reaching for the highest yield. A bond fund yielding far more than the rest is almost

always taking more risk — long duration, junk credit, or both. That extra yield is payment for risk, not a free lunch.

• Ignoring duration. Two funds can both be "bond funds" yet behave completely

differently. TLT can swing several times as much as a short-term fund for the same rate move. Always check duration before you buy.

• Confusing distribution rate with SEC yield. The trailing payout can look higher or

lower than what the fund is actually earning today. Compare the 30-day SEC yield for a fair, standardized number.

• Expecting a fixed payback like a single bond. A bond ETF has no maturity date and no

promised return of a set dollar amount. If you specifically need $10,000 on a known future date, an individual bond or CD does that; an ETF does not.

• Skipping bonds entirely because "yields are low." Even modest bond income plus the

diversification benefit can meaningfully steady a stock-heavy portfolio, especially near or in retirement.

FAQ

Do bond prices fall when rates rise?

Yes — this is the core rule of bond investing. A bond's coupon is fixed, so when market interest rates rise, newly issued bonds pay more and existing lower-coupon bonds become less attractive. Their prices fall until their yield matches the new going rate. The opposite is also true: when rates fall, existing bonds with higher coupons become more valuable and their prices rise. How much a bond or fund moves depends on its duration — long-term bonds like TLT swing far more than short-term bonds for the same rate change. This inverse price-yield relationship applies to individual bonds and bond ETFs alike.

Are bond ETFs safe?

It depends entirely on what the ETF holds. A broad, high-quality fund like BND or AGG — mostly Treasuries and investment-grade corporates — carries very little default risk, but its price still floats with interest rates and can fall in a year when rates rise. A long-term Treasury fund has almost no default risk but big rate-driven price swings. A high-yield ("junk") bond fund carries real default risk and can drop alongside stocks. So "safe" is relative: bond ETFs are generally lower-risk than stocks, but they are not guaranteed and can lose value. Match the fund's credit quality and duration to how much risk you want.

What's the difference between yield-to-maturity and current yield?

Current yield is simply the annual coupon divided by the price you paid — a quick snapshot that ignores what happens at maturity. Yield-to-maturity (YTM) is the total annualized return if you hold the bond until it matures, including both the coupons and any gain or loss between your purchase price and the $1,000 par you receive at the end. YTM is the more complete and comparable figure for individual bonds. For a bond *ETF*, you instead compare the standardized 30-day SEC yield, which annualizes the fund's recent net income under uniform SEC rules.

How is a bond ETF different from owning a single bond?

A single bond has a fixed maturity date when you get your exact par value back, so short- term price moves do not matter if you hold to the end. A bond ETF never matures — it continuously replaces maturing bonds — so its price, tracking its NAV, floats permanently with interest rates and offers no promised payback amount on a set date. In exchange, the ETF gives you instant diversification across thousands of bonds, monthly income instead of semiannual coupons, and the ability to buy or sell anytime the market is open. You trade certainty of return for simplicity and liquidity.

What is a good yield for a bond ETF?

There is no single "good" number, because a bond ETF's yield reflects its risk. A broad, high-quality fund typically yields close to prevailing intermediate Treasury and investment-grade rates. A fund yielding much more is almost certainly taking on longer duration, weaker credit, or both — that extra yield is compensation for risk, not a bonus. The right yield is the one whose underlying risk matches your goals. Compare funds using the 30-day SEC yield so you are measuring the same thing, and always check duration and credit quality alongside the headline number.

Should I hold bonds if I'm focused on dividends?

Often, yes. Even a dividend-focused investor benefits from some bond exposure because bonds do jobs dividend stocks cannot: their coupon income is contractual and more predictable than a dividend, and high-quality bonds tend to hold up or rise when stocks fall, cushioning your portfolio in a downturn. A core bond ETF like BND can steady the ride and provide reliable monthly income, which is especially valuable near or in retirement. How much to hold depends on your time horizon and risk tolerance — younger investors may hold little, while retirees drawing income often hold significantly more.