A ladder's length sets how many years it covers and how many rungs it wants, while the inflation assumption uplifts each year's target income — and because the gilt universe has gaps, some years resolve to no conventional gilt and the rung stays empty.
Length sets the window
A ladder's length is the number of years it runs for, and it decides how many year bands the window contains and therefore how many rungs the ladder wants — one per band. On the bond ladder designer the length control opens on five years and is bounded at twenty, so a ladder is a short run of consecutive years rather than an open-ended plan. Each band asks for the conventional gilt whose maturity lands in that year; the ladder is the set of those gilts laid end to end.
Length is a design choice about how far forward the ladder reaches, not a measure of its quality. A longer ladder spreads the same purpose over more years and more rungs; a shorter one concentrates it. What length does not do is change the gilts on offer in a given band — that is set by the gilt universe, which the next sections come to.
The inflation assumption uplifts each year's draw
The income the ladder is asked to pay is an inflation-adjusted target, so the page raises it year by year at an inflation assumption. If the first year's target is set, the second year's is that figure uplifted once, the third twice, and so on. The factor for year k is one plus the assumed rate, raised to the power of the years elapsed. This inflation assumption is a stated input, not a forecast: it is the reader's assumption, or the page's documented default, and a different assumption produces a different set of yearly draws.
The income target mode deflates its real-terms chart at a fixed 3.0 per cent a year real assumption, while the lump sum mode uplifts and deflates at the inflation figure the reader enters. Either way the rate is an assumption the arithmetic is run on, so the figure it produces is only as good as the assumption stated beside it.
Why some years resolve to no gilt
The gilt universe does not have a conventional gilt maturing in every calendar year. For a given band the page looks for a conventional gilt whose maturity lands in that year or, failing that, one still running that matures nearest to it — but if no candidate qualifies, the band resolves to nothing. That year then carries an empty rung: the window's column is still shown so the years stay aligned, but the year contributes no income, because no gilt was found to fund it. This is a real property of the gilts in issue, not a fault in the page, and it is the single thing most likely to surprise a reader who assumes a rung per year is always available.
An empty rung also changes the sizing, because the divisor that spreads the lump sum across the ladder sums only the rungs that resolved. The years that did resolve are sized to fund their own draws; the empty year simply has nothing funding it, and the income projection for that column falls away. Reading the projection year by year, rather than only the ladder total, is what makes an empty rung visible.
Length and uplift worked through
The table is an illustration, not a quote from any gilt. It assumes a first-year target income of £10,000, an inflation assumption of 3.0 per cent a year, and a five-year window, and marks an empty rung in the final band to show what one looks like. The uplift arithmetic is exact; the gilts and the resolved-or-empty pattern are illustrative.
| Year | Band | Uplift factor at 3.0 per cent | Target draw | Rung resolved? |
| 1 | first band | 1.000000 | £10,000.00 | Yes |
| 2 | second band | 1.030000 | £10,300.00 | Yes |
| 3 | third band | 1.060900 | £10,609.00 | Yes |
| 4 | fourth band | 1.092727 | £10,927.27 | Yes |
| 5 | fifth band | 1.125509 | £11,255.09 | No — empty rung |
Each factor is 1.03 raised to the year number: 1.03 squared is 1.0609, cubed is 1.092727, and to the fourth power is 1.125509. Multiplied by the £10,000 first-year target, those give the yearly draws shown. The fifth band is marked empty to make the point that a target can be stated for a year the gilt universe cannot fill; the per-gilt schedule that a real rung is sized from is on a gilt's own page, opened from the conventional gilts list.
What length and the assumption do together
Length and the inflation assumption compound in the arithmetic. A longer ladder asks for more years of rising draws, so the later years' targets are the largest and the ladder's total demand is set by the last year it covers. A higher assumed inflation makes every later year larger still. And a longer window is also more likely to meet a year the gilt universe cannot fill, so lengthening a ladder raises both the income it asks for and the chance of an empty rung. None of that makes a longer ladder wrong; it makes the year-by-year projection the honest thing to read.
Background, not advice
This article explains how the ladder designer's length control and inflation assumption shape the rungs, and why some years resolve to no conventional gilt. It is general background on how the figures are put together, not investment, tax or legal advice for any reader's circumstances. The inflation rate is an assumption the arithmetic is run on and not a forecast, and the figures above are illustrative and state their inputs. The primary source for a real gilt's maturity, coupon and cash-flow dates is the gilt's own record and the Debt Management Office.