The DMO yield and the annual figure, compared

The DMO yield follows the gilt market's twice-yearly, actual-days convention while the annual figure compounds once, and the two differ by an amount that grows with the level of the yield.

Two ways to state one quantity

A gilt's redemption yield is a single quantity: the rate at which its remaining payments discount back to the price. There is more than one way to write that rate down, and the two on the conventional gilts list are the market's and the annual one. The DMO yield follows the UK Debt Management Office's convention — coupons twice a year, days counted on the actual calendar — and the gross yield compounds once a year. The same gilt, the same cash flows, two spellings.

Neither spelling is more accurate than the other, and neither is a different estimate of the future. They differ only in the compounding they assume, which is a presentational choice with a small, predictable arithmetic consequence. Knowing which is which is what stops a reader treating a few basis points as a market signal.

What the DMO convention does

A conventional gilt pays its coupon in two instalments a year, and the DMO convention discounts each payment by the actual time between settlement and that payment, compounding twice a year. That matches the instrument: the cash arrives semi-annually, so the rate is solved semi-annually on the days the payments actually fall. The day count is actual rather than an assumed half-year of 182.5 days, which matters for a gilt whose coupon dates are unevenly spaced or whose period is shortened by its issue date.

Because it follows the gilt's own payments, the DMO convention is the one the market quotes and trades on. A dealer quote, a market screen and a provider's reference yield are all stated on a semi-annual basis, so a figure compared with any of them should be the DMO figure rather than the annual one.

What the annual figure does

The annual figure answers a different need: a return that can be compared with anything quoted once a year. Savings rates, fund returns and annual reports are stated on an annual footing, and a semi-annual figure placed beside them would compare two different bases even before any tax is considered. Compounding the yield once a year puts it on the same footing.

The site treats the annual figure as its headline and shows the DMO figure beside it, so a reader has both without a conversion step. The modified duration column is on the annual basis too, so it shares a basis with the yield it sits beside rather than with the DMO column.

The arithmetic between them

Compounding twice a year at half the annual rate produces slightly more than compounding once at the full rate, because the first half-year's interest earns interest in the second. The annually compounded equivalent of a semi-annual yield y is y plus y squared over four. The gap therefore grows with the square of the level: small at low yields, larger at high ones, and never a constant number of basis points.

The three pairs are illustrative conversions rather than yields from any gilt, and each is stated with its input. Two things follow from the table. The first is that the annual figure is always the higher of the two for a positive yield. The second is that the size of the gap tells a reader nothing about the gilt, only about the level of its yield — so a gap that changes between two rows is not evidence of anything except different yields.

Do not correct one column into the other by adding a fixed number of basis points. The gap is a function of the yield, so a fixed adjustment is right at one level and wrong at another.

Where the convention changes at the short end

A gilt with a year or less to run has no full half-year of coupon left to compound over, and the site's calculation reads its yield on a money-market basis instead: a simple rate over the actual days to each remaining payment, on a 365-day year. That is a different convention from the semi-annual one and a different one again from annual compounding, and it applies to the gilt rather than to the reader's choice.

The practical consequence is that a gilt very close to maturity is not directly comparable with one several years out on a like-for-like basis, even though both show a gross and a DMO figure. The report records the calculation version that produced each stored figure, and the help and user guide explains how to read that stamp; a reader comparing a short gilt with a long one should check it rather than assume one convention throughout.

Which figure to quote

Quote the DMO figure when the comparison is with the market: a dealer, a screen, a provider's reference yield or another gilt's DMO figure. Quote the annual figure when the comparison is with an annual return, a savings rate or the site's own modified duration and net columns. Quote either, but name it, because an unnamed yield is a number a reader has to guess the basis of.

The curve page takes the same care internally: before differencing a gilt's yield against the fitted benchmark, it puts both legs on one basis, so a spread in basis points reflects the gilt against the curve rather than one convention against another. That is the pattern to copy when comparing any two yield figures from different sources.

Background, not advice

This article explains the difference between the DMO yield convention and the annual figure; it is general background, not investment, tax or legal advice for any reader's circumstances. The conversions above are illustrative and state their inputs, and a yield moves with the price, so a figure read on one date will differ from the next. The Debt Management Office and the daily report named on the page are the primary sources for a real yield and the convention it carries.