Lengthening a ladder spreads the same lump sum over more rungs, so a fixed amount stretched across more years affords a smaller income each year but pays it for longer — and the gilt curve decides how much a longer rung yields.
Length changes the split, not the money
A ladder of a given length splits a lump sum into that many rungs. Hold the lump sum fixed and lengthen the ladder, and the same money is divided among more years, so each rung is smaller and the income each year affords falls. That is not a defect of a longer ladder; it is what dividing the same total more ways does. A shorter ladder concentrates the money into fewer, larger rungs; a longer one spreads it thinner and further.
The length control on the bond ladder designer sets how many year bands the window holds, and therefore how many rungs the lump sum is shared across. Reading length as a way to get more income per year gets the relationship backwards: for a fixed lump sum, more length means less income each year, over more years.
Income per extra rung
It helps to think in terms of the marginal rung. Add one year to the ladder and one more rung joins the set, taking a share of the same lump sum and being sized to fund that year's draw. The other rungs then carry a slightly smaller share, so the per-year draw eases down a little as the ladder grows. The income the extra rung brings is not extra income in the first year; it is the same money repurposed to cover one more year later on. Over the whole ladder the total income roughly holds, but its per-year size and its span both change. A worked sense of it: if five years split £50,000 into five rungs of about £10,000 each, six years splits the same sum into six smaller rungs, and the per-year draw falls by roughly the share the sixth rung takes from the other five.
A rough division, before the detail
As a first check, before the gilts' prices, the inflation uplift and their yields, a lump sum divided by the length gives a rough annual draw. The table takes a notional £50,000 and divides it across three lengths. The division is illustrative only; the designer's real figures differ because each rung is priced and uplifted, but the direction they move in is set by the division.
| Length | £50,000 divided by length | Rough annual draw | Years it covers |
| 5 years | £50,000 ÷ 5 | ≈ £10,000 | 5 |
| 10 years | £50,000 ÷ 10 | ≈ £5,000 | 10 |
| 15 years | £50,000 ÷ 15 | ≈ £3,333 | 15 |
The arithmetic is plain: £50,000 across five years is about £10,000 a year, across ten is about £5,000, across fifteen is about £3,333. Halving the annual draw broadly doubles the number of years it is paid. What the rough division cannot show is the effect of the gilts themselves, which the next section comes to.
What the gilt curve adds
The rough division ignores yield, but longer gilts often yield more than shorter ones, because the market usually asks a higher return for tying money up for longer. If it does, a longer rung bought at a lower price for the same redemption earns a higher gross yield, which works against the thinning the division describes. The gilt yield curve plots every priced gilt against its maturity, so a reader can see whether the longer rungs a longer ladder reaches actually yield more — and by how much. Where the curve is flat or inverted, the extra length buys little or no extra yield to offset the smaller per-year draw.
So length and the curve act together. Length decides how the lump sum is divided; the curve decides what each rung yields. A longer ladder spreads the money thinner but may reach higher-yielding gilts; a shorter one concentrates it in fewer rungs that may yield less. Neither dominates: they trade one effect against the other, which is why the page shows the resulting per-year draw rather than leaving a reader to guess it from length alone.
Reading the trade-off
The trade-off is between the size of the annual income and how many years it lasts. A short ladder pays a larger income for fewer years; a long one pays a smaller income for more years, and reaches further out along the curve. Which is apt depends on how many years a reader wants covered, not on which length is somehow better. The figure worth reading is the per-year draw at each length beside the number of years it covers, and the curve for what the longer rungs yield. A reader who wants a decade of income and a reader who wants a large income for five years are asking different questions, and length is the control that answers each.
Background, not advice
This article explains how ladder length and income relate for a fixed lump sum, and how the gilt curve modifies the picture. It is general background on how the figures are put together, not investment, tax or legal advice for any reader's circumstances. The rough division above is illustrative and states its inputs; the designer's real figure accounts for each gilt's price, the inflation uplift and its yield, and a reader's own numbers will differ. The primary source for a real gilt's price and yield is the gilt's own record and the day's market data.