Bond ETFs Explained

Bonds aren't the safe asset the brochure suggests

Bonds get sold as the calm half of a portfolio. They're more layered than that. Duration risk can produce equity-sized drawdowns, credit risk shifts the asset toward equity behavior, and the negative correlation with stocks that the standard 60/40 framing relies on only shows up in certain regimes.

How a bond ETF works

A bond ETF holds hundreds or thousands of bonds inside an exchange-traded wrapper. Coupons are distributed monthly. As bonds mature, the fund reinvests at whatever rate the market offers.

That rolling structure changes how to read the yield. An individual bond held to maturity locks in its yield. An ETF rolls constantly, so today's quoted yield is what you'd earn if rates stayed flat. They rarely do.

The wrapper buys intraday liquidity, automatic diversification across hundreds of issuers, and explicit duration and credit reporting on the daily fact sheet. Both BND (Vanguard Total Bond Market) and AGG (iShares Core US Aggregate) publish these.

The retail bond market is mostly closed

Buying a single corporate or municipal bond is harder than buying a single stock. The underlying market is hostile to small lots.

Most US corporate bonds quote in $1,000 face value increments, with retail dealer minimums commonly $5,000 to $10,000 per ticket. Primary issuance is allocated to institutional buyers in $1 million "round lots"; retail picks up the leftovers in the secondary market. A diversified ladder of 20 to 30 names starts at roughly $200,000 to $500,000 in capital, before any credit work.

The secondary market is expensive too. Edwards, Harris, and Piwowar (2007) documented one-way trading costs around 140 basis points on small retail trades, falling sharply as trade size climbed toward institutional round-lots. Bessembinder et al. (2018) found the gap had narrowed but not closed. A BND share trades on exchange at a spread of 1 to 2 basis points. The cost difference between $10,000 of BND and $10,000 face of a single corporate bond can run in the hundred-basis-point range before either trade settles.

Operational friction stacks on top. Coupons and maturities arrive on dozens of dates, each forcing a manual reinvestment. The ETF rolls this automatically.

The one direct-bond door open to retail is government paper. TreasuryDirect and equivalent national auctions let individuals buy at institutional pricing. Even there, building and rolling a 30-bond ladder is operational work most people abandon within a few years.

For most individuals, an ETF is the practical access point. Direct bonds assume a balance sheet and an operations team retail doesn't have.

Duration: the one number that matters most

Duration is a sensitivity measure. A fund with duration 6 loses roughly 6% if rates rise 1 percentage point, and gains 6% if rates fall 1 point. Duration 15 doubles those.

This is why a "boring" Treasury fund can move like a stock. TLT holds 20+ year Treasuries with a duration around 17. When the Fed hiked policy rates from near zero to 5.50% between 2022 and 2023, TLT fell close to 50% from peak. The credit didn't change. The math of long duration did.

Match the fund's duration to your time horizon. Cash you'll need within 12 months belongs in money market or T-bill ETFs, where duration is measured in weeks. Money you won't touch for a decade can tolerate intermediate duration (BND, AGG, both around 6). Pure long-duration funds like TLT are a rate bet dressed up as a passive bond allocation.

Credit quality, in tiers

Bond ETFs slot into a credit ladder. Each rung pays for taking more default risk.

Developed-market sovereigns sit at the top, with no meaningful default risk. BND and AGG hold heavy US Treasury weights; pure-Treasury funds like GOVT and TLT carry no corporate exposure at all.

Investment-grade corporate bonds (LQD, VCIT, VCSH) pick up 60 to 120 basis points over Treasuries by lending to the largest, most stable companies. Moody's puts the long-run annual default rate for IG issuers at around 0.1%.

High-yield (junk) bonds — HYG, JNK, USHY — pay another 200 to 400 basis points against historical default rates around 4%. The premium roughly compensates for losses across full cycles. In a recession defaults spike ahead of the yield, which is why high yield trades more like equity than like Treasuries.

Past that sit emerging-market sovereign bonds (EMB), preferred stock (PFF), and bank capital instruments. Each trades idiosyncratic risk for yield, and each looks less like a bond and more like equity.

Yield vs price: what total return is

Total return is coupon income plus price change. Coupon income is roughly predictable from yield-to-maturity. Price change is governed by duration and the path of rates.

Two yield numbers appear on most fact sheets.

SEC yield (or yield-to-maturity) is forward-looking: the yield you'd earn if you bought today and rates stayed flat. Use this for projecting return.

Distribution yield is backward-looking: the trailing twelve months of distributions divided by today's price. In a rising-rate environment it understates what the fund pays going forward; in a falling-rate environment it overstates.

Starting yield-to-maturity is the best predictor of a bond fund's return over a holding period roughly equal to its duration. Antti Ilmanen documents this in Expected Returns (2011). A BND with a 5% SEC yield and duration 6 delivers close to 5% per year over the next six years, absent extreme rate moves; at 1.5%, close to 1.5%. The fact sheet quotes forward returns directly.

What role bonds play in a portfolio

Bonds do several jobs at varying reliability. Conflating them is the most common allocation mistake.

Income predictability is the one bonds deliver consistently. A broad fund yielding 4.5% returns close to that over a holding period near its duration. Equity returns over similar windows are far more dispersed.

Volatility dampening comes next. Bond drawdowns are smaller than equity drawdowns on average, which softens portfolio swings even in years when bonds don't actively offset losses.

The role most retail commentary leans on is the negative-correlation hedge: bonds rallying when stocks fall, the classic 2008 picture. It works when equity drawdowns are driven by growth scares and the central bank cuts. It fails when drawdowns are driven by inflation shocks and rates rise alongside falling stocks.

Where alternatives do parts of the same job

For inflation, TIP (Treasury Inflation-Protected Securities) adjusts principal with CPI and hedges the realized component directly. It doesn't hedge real-rate shocks, so when real rates rise sharply TIPs can fall alongside nominal Treasuries. Gold ETFs (GLD, GLDM) are the longer-running inflation and crisis hedge with no duration sensitivity. Commodities (DJP, GSG) cover supply-side inflation from a different angle.

For real diversification (the property bonds keep claiming and intermittently delivering), managed futures funds (DBMF, KMLM) trade trends across major asset classes and have historically delivered positive returns when 60/40 portfolios failed in inflation shocks. The cost is higher (0.85% to 1.10% TER), but the diversification is regime-agnostic in a way that bonds historically haven't been.

For safety on a sub-12-month horizon, money market or T-bill ETFs deliver the cash-equivalent job without the rate-sensitivity of an intermediate-duration bond fund.

None of these replaces bonds wholesale. Each covers a specific slice, and the right blend depends on which slice matters most.

How to pick one

For most passive portfolios, one broad bond fund is enough. BND and AGG hold near-identical baskets (intermediate-duration investment-grade US bonds, mostly Treasuries and agency MBS) at around 0.03%. For global diversification, BNDW bundles US and international bonds roughly half-and-half at 0.05%. UCITS investors get similar exposure through AGGG or VAGF.

Tilts come second. Worried about inflation? Add a slice of TIP. Hedging a long horizon against falling rates? Lean on TLT, accepting equity-like volatility. Extra yield through a small high-yield satellite (USHY, HYG), with drawdown behavior that tracks equities. None of these belong in the core.

The harder discipline is staying allocated through years where bonds lag equities. Index funds beat most active managers in fixed income too, and SPIVA's bond scorecards confirm it. Coverage of the asset class at minimum cost, held through the cycle.

If you'd rather sort the universe yourself, the fixed-income side of the screener narrows to bond funds, sortable by expense ratio or AUM. Focus tags like CLO or CoCo Bonds isolate specific subtypes. Match the fund to the role. Best-ticker hunting is a distraction.