What it means
Buying bonds directly is awkward for most investors. Minimum trade sizes are often large, prices are negotiated rather than displayed, and building a spread of maturities and issuers takes real money and real effort.
A bond ETF packages that work into one instrument that anyone can buy in small amounts. Most bond ETFs track an index, such as a broad government bond index or an investment grade corporate index, and hold a representative sample of it.
Others are actively managed, with a team choosing the holdings. Either way the fund receives coupon payments from its bonds and passes them on to holders, usually as a monthly or quarterly distribution.
The single most useful number for comparing bond ETFs is the yield, but you have to read which yield is being shown. A standardised 30 day yield is calculated after fees and is designed for comparison, while a simple distribution yield reflects what was actually paid out recently and can be flattered by the fund's holdings of high coupon bonds bought above face value.
Duration, which measures sensitivity to interest rate moves, is the other number that matters. Unlike an individual bond, a bond ETF has no maturity date.
An individual bond eventually repays its face value, which gives a nervous investor a date to hold on to, whereas an ETF simply keeps replacing bonds as they mature and its price keeps moving with interest rates. Target maturity bond ETFs are a variant designed to close that gap by holding bonds that all mature in the same year.
Liquidity is the feature people misunderstand most. The ETF's shares can trade actively even when the underlying bonds do not, which is genuinely useful, but in stressed markets the ETF price can move away from the calculated value of its holdings.
That gap, a discount or premium to net asset value, tends to widen exactly when investors most want to sell.
In practice
Real-world examples.
Example
A small business owner with $60,000 of long-term savings buys a broad government bond ETF rather than trying to pick individual bonds. One trade gives exposure to hundreds of issues across a range of maturities.
Example
A corporate treasurer parks part of a cash reserve in a short duration investment grade bond ETF, accepting modest price movement in exchange for a yield above the company's bank deposit rate. The policy caps the holding at 20% of surplus cash because the value can fall.
Example
A pension trustee compares two corporate bond ETFs tracking the same index and finds identical holdings but expense ratios of 0.09% and 0.25%. On a $40,000,000 allocation the difference is $64,000 a year, so the cheaper fund is selected.
Formula
Calculation
Net asset value per share = (Total fund assets - Total fund liabilities) / Shares outstanding. Net yield to the investor = Gross portfolio yield - Expense ratio.
A corporate bond ETF holds $840,000,000 of bonds and accrued income, owes $4,000,000 in payables and accrued fees, and has 8,000,000 shares outstanding.
Net asset value per share = ($840,000,000 - $4,000,000) / 8,000,000 = $836,000,000 / 8,000,000 = $104.50
An investor buys 200 shares at that value, costing 200 x $104.50 = $20,900.
The portfolio's gross yield is 4.35% and the fund's expense ratio is 0.15%, so the net yield is 4.35% - 0.15% = 4.20%.
Gross income on the holding = $20,900 x 4.35% = $909.15
Annual fee borne = $20,900 x 0.15% = $31.35
Net expected annual income = $909.15 - $31.35 = $877.80, which matches $20,900 x 4.20% = $877.80.
That $31.35 fee looks trivial, but on a $2,000,000 corporate cash reserve the same 0.15% would cost $3,000 a year, which is why expense ratios deserve attention at scale.Case study
Seen in the real world.
Lantern Point Foundation is an invented charitable endowment used here purely as an illustrative example. Its investment committee moved $10,000,000 from individual corporate bonds into a bond ETF, mainly because administering forty separate holdings had become a burden for a two person finance team. The move cut settlement work sharply and made monthly valuation straightforward.
Eighteen months later, during a sharp rise in interest rates, the committee grew uncomfortable. The individual bonds they had previously held would have been carried to maturity and repaid at face value, whereas the ETF simply showed a lower price with no date on which anything would be repaid. Several trustees asked whether the fund had performed badly.
In this illustrative case nothing had gone wrong: the ETF's price decline reflected the same interest rate move that would have reduced the market value of the old individual bonds, which had simply been less visible on the books. The committee added a short note to its reporting explaining duration and price sensitivity, and split the allocation between a short duration fund and a target maturity fund so that part of the portfolio still had a defined repayment date.
Watch out
Common mistakes.
- Treating a bond ETF as equivalent to holding bonds to maturity. The fund has no maturity date, so there is no point at which face value is repaid to the holder.
- Assuming a bond fund cannot lose money. Bond prices fall when interest rates rise, and a longer duration fund can post a sizeable loss in a year of rising rates.
- Choosing a fund on distribution yield alone. A high distribution can come from bonds bought above face value, whose premium is gradually lost, so a standardised after-fee yield is the fairer comparison.
Questions
People also ask.
What does duration tell me?
It estimates the percentage price change for a one percentage point move in interest rates, so a fund with a duration of six would fall roughly 6% if yields rose by one point.
Why can the ETF price differ from the value of its holdings?
The shares trade continuously while many underlying bonds trade rarely, so in stressed markets the traded price can sit at a discount or premium to net asset value.
Is a bond ETF suitable for corporate cash management?
A short duration fund can work for cash that is not needed immediately, but it is not a deposit substitute, because the value can fall between purchase and sale.
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