The Change column on a gilt row records how far the yield moved between two stored reports, and reading it correctly means knowing which two reports and what a blank cell means.
Two reports, one difference
The Change column on the conventional gilts list is a subtraction. It takes the yield in the current report and subtracts the yield in the most recent earlier report that carried the same gilt, then states the difference in basis points. The prior side is found by looking back over the five business days before the report and taking the most recent that priced the same gilt, matched by its identifier rather than by its position on the list. A gilt that moved up or down the sort order therefore does not acquire a spurious change, and a report that was not built on a given day is skipped in the search.
One day is not always one calendar day. The comparison is always against a stored report, so the figure never depends on a live feed or on the moment the page was opened; the same report produces the same change whenever it is read. Reports are built on London business days, so a report for a Monday is compared with the previous business day's report, which is usually a Friday. After a bank holiday the gap is longer, and the change in the cell spans the whole break rather than a single session. The figure is still a genuine change between two stored dates; it is just not a claim about a fixed 24 hours.
Basis points, and why the unit is used
A basis point is one hundredth of a percentage point, so a yield that moves from 4.00% to 4.10% has moved by ten basis points. The unit exists because day-to-day yield moves are small: stated in percentage points, most of them would need two decimal places to say anything at all, and the trailing zeros invite a reader to compare figures that are effectively the same. Basis points keep the magnitude visible at the scale the market actually moves.
| Yield moved from | Yield moved to | Change shown |
| 4.00% | 4.10% | +10 basis points |
| 4.00% | 3.95% | −5 basis points |
| 4.00% | 4.00% | 0 basis points |
| 4.00% | no earlier report | Blank |
The sign follows the yield, not the price. A positive change means the yield rose, which for a fixed-coupon gilt means the price fell, and a negative change means the yield fell and the price rose. A reader who reads the Change column as a price movement will have the sign backwards on every row.
What a blank cell means
Not every gilt has a previous observation to compare with. A gilt issued since the last report has no earlier figure, and a gilt the earlier report did not price — because it was outside the source's coverage that day — has nothing to subtract. A row whose earlier figure was priced from a different source is also left without a change, so that a change of feed is not reported as a move in the gilt. In every case the cell is left empty rather than filled with zero, because zero would assert that the yield did not move, and that is a different claim from not knowing.
The blank is therefore information about the record rather than about the gilt. It is the same principle as an empty page rather than a stale price: where the site does not have the comparison, it says nothing instead of inventing a neutral value. A reader scanning for movement should treat blanks as missing data and count only the rows that carry a figure.
Reading the column as a whole
One row's change is a number; a column of changes is a description of a session. If most of the priced gilts show a positive change, the market repriced upward across the curve. If the changes are scattered in sign, the session was mixed and the movement was local to particular gilts or maturities. The list does not compute that summary for the reader, but the two Since the previous close views do split the rows into the gilts that moved each way, which is the same information at a glance.
- Count only the rows that carry a figure when judging the breadth of a move.
- Compare the size of the changes as well as the sign: a column of one-basis-point moves is a different session from a column of ten.
- Read a row's change against the curve's move for the same date before calling it a local event.
- Treat a single session as a measurement, not as the start of a trend.
One day against a year
The Change column answers what happened between two reports. It cannot say whether the move was large or small for the gilt, because that depends on the range the gilt has traded in. The trend column and the price history on a gilt's own page, reached from the list, supply that context: the history chart defaults to a trailing twelve-month window and plots the stored clean price and yield, so a day's change can be read against a year of them.
The gilt yield curve supplies the other half of the context: it shows where the gilt's yield sits relative to its fitted benchmark on the same date. A ten-basis-point change that keeps the gilt at the same spread to the curve is the market moving; the same change while the curve stayed still is the gilt moving. The daily change column records the move, and the other two pages say what it was part of.
Background, not advice
This article explains how the one-day yield-change figure is produced and read; it is general background, not investment, tax or legal advice for any reader's circumstances. A change between two reports describes a past session and says nothing about the next, and a price that has moved is not a realised gain or loss unless the gilt is sold. The daily report and the gilt's own stored history are the primary sources for a real yield or change.