The figures on this site come from a simulation model of the State Pension built by the Centre for British Progress. It forecasts inflation and earnings growth 10,000 times, applies each uprating rule to every forecast, and costs the difference from the Triple Lock in each year to 2049/50. By default every alternative takes effect from the April 2030 uprating, with the Triple Lock applying to the 2027, 2028 and 2029 upratings under every option. That matches the Prime Minister's plan, announced on 29 September 2026, to replace the Triple Lock from April 2030 with a design that follows the Resolution Foundation's Smoothed Triple Lock. The slider at the top of the Solutions page moves the start to any uprating from April 2027 to April 2034; the Triple Lock applies to every earlier uprating. The rules were last changed on 5 October 2026 and the figures were exported on 6 October 2026, using ONS data up to April 2026.
Changes since launch. The model was updated on 1 October 2026: the CBP Lookback Reform's window now compares the same years for pensions and earnings, the income tax calculation follows the shift of pensioners onto the new State Pension, and the horizon runs to 2049/50. These changes moved the published figures, and the savings charts now show totals before and after income tax. On 5 October 2026 the RF Smoothed Triple Lock's earnings path was corrected to fall in a year when earnings fall; it had been held flat, which overstated the path after every earnings fall and so overstated that option's cost. The same update added the CBP Lookback + 2.5% Floor as an option. On 6 October 2026 the "What determines the uprating each year?" chart in each option's detail panel was redrawn as one column per April uprating, and each year is now classified against the elements of that option's own rule: a Lookback catch-up that happens to equal that year's earnings growth is shown as a catch-up, a year in which the pension is held flat (0%, because prices or earnings fell) is shown separately, and the Leunig option's floor is shown at its own 2%. The same day the Solutions page gained a slider for the year the alternatives take effect, from April 2027 to April 2034 (the Prime Minister's April 2030 by default); the model is run once per start year on the same 10,000 economic paths.
The Triple Lock uses two readings each year: CPI inflation in September, and growth in average weekly earnings over May to July. Both are published by the ONS. The model forecasts them from a monthly statistical model fitted to 303 months of ONS data, from February 2001 to April 2026: the CPI index (series D7BT) and the level of average weekly earnings, total pay (series KAB9).
The model works in month-on-month changes rather than annual rates. Consecutive annual rates share eleven months of data, so a model fitted to them mistakes that overlap for persistence and produces forecasts that are too smooth. Month-on-month changes do not overlap. Each simulated path is turned back into a September CPI rate and a May to July earnings rate by compounding twelve months at a time, the same construction the ONS uses. Applied to the historical data, this reproduces the published September CPI rate exactly, and the published May to July earnings rate to within 0.13 percentage points.
Monthly inflation depends on its own value one, six and twelve months earlier. The six- and twelve-month terms pick up seasonal patterns, since the CPI index is not seasonally adjusted. Monthly earnings growth depends on its own value in the previous month and on inflation in the previous one and two months. Earnings do not feed back into inflation. This link matters for the Triple Lock: an inflation shock that sets one year's uprating also pushes up the earnings reading that can set the next.
Each forecast adds random shocks, drawn from a normal distribution whose size is estimated from the historical data. Drawing 10,000 sets of shocks gives 10,000 monthly paths for inflation and earnings from May 2026 to 2049. Every uprating rule on this site is applied to the same 10,000 paths, so the differences between rules come from the rules themselves, not from different draws.
Normal shocks understate how often large inflation surprises happen. In the simulations, September CPI has a standard deviation of 1.78 percentage points, against 2.24 in the historical data, so an episode like 2022–23 comes up less often than history suggests. The Triple Lock pays the highest of three measures, so it gains most from large shocks. The model therefore probably understates both the cost of the Triple Lock and the savings from replacing it.
Spending in each year is the number of pensioners on each type of State Pension, multiplied by the full weekly rate for that type: £241.30 for the New State Pension and £184.90 for the Basic State Pension in 2026/27, uprated each year by the rule being tested. Using full rates ignores partial entitlements, and the additional State Pension, which rises with CPI rather than the Triple Lock. The savings scale with this spending base, so they carry the same approximation.
The two types matter because they pay different amounts. The Basic State Pension covers people who reached State Pension age before April 2016, and the New State Pension covers everyone since. Nobody new joins the Basic State Pension, so the model projects it as a closed group that shrinks with mortality. The New State Pension gains everyone reaching State Pension age, with take-up of 96.8% calibrated to DWP's November 2025 caseload. State Pension age rises from 66 to 67 between 2026 and 2028, as set by the Pensions Act 2014, which slows the inflow for two years. The New State Pension overtakes the Basic State Pension in 2029, and by 2049 it covers 15.4 million people against 0.3 million.
Projected number of pensioners by state pension type, 2026–2049
Chart: Centre for British Progress · Source: DWP Stat-Xplore caseload, ONS National Population Projections (2022-based) · CBP analysis
The saving in each year is spending under the Triple Lock minus spending under the alternative, on the same forecast path, averaged across all 10,000 paths. Charts show this in cash terms. Totals are also given as a present value in 2026 prices: each year's saving is deflated by that path's own CPI and then discounted at 3.5% a year, the real discount rate in HM Treasury's Green Book. Where ranges are shown, they run from the 10th to the 90th percentile of paths (the middle 80%), for the savings and for the pension's path alike.
Every total on this site runs from the first reformed uprating (2030/31 by default; the Solutions page's slider moves it between 2027/28 and 2034/35) to 2049/50, and the end year matters. An earlier start has more years of savings in the total as well as an earlier divergence from the Triple Lock. The gap between the Triple Lock and any alternative widens every year, because the Triple Lock keeps lifting the pension relative to earnings, while spending itself grows with earnings and with the number of pensioners. So the saving in each year grows faster than the 3.5% discount rate for several decades, and a longer horizon would give a larger present value. The totals are the saving over the next twenty years, not a steady-state figure.
A higher State Pension raises more income tax, so part of each saving comes back to the Exchequer anyway. The net figures subtract that tax. The model takes each pensioner's own taxable income from the Family Resources Survey 2024/25, grows the State Pension part with the uprating rule and the rest with earnings, and applies income tax at 20%, 40% and 45%. Thresholds stay frozen until 2030/31, as announced at Budget 2025, and rise with CPI after that, the default in the Income Tax Act 2007; the additional-rate threshold has no indexation in law and stays fixed. About 3.9% of State Pension spending goes to people living abroad (DWP figures for 2024/25), who generally pay tax in their country of residence, so that share is left out of the tax calculation.
As a check, the survey puts 68.4% of people over State Pension age above the Personal Allowance. HMRC's count of 9.08 million taxpayers over State Pension age in 2025/26 implies about 67.8%. The tax comes to about 20% of the gross saving in the early 2030s and 22% by the late 2040s, with little difference between the alternatives. It rises over time because the full new State Pension already sits at the Personal Allowance, so almost every extra pound of it is taxed, and because more pensioners retire onto the new State Pension each year. Income other than the State Pension is assumed to grow with earnings: as each new cohort retires with larger private pensions than the one before, the average pensioner's other income tracks earnings rather than prices.
Each alternative is a rule that turns the year's CPI and earnings readings, and for some rules past readings, into that year's uprating. Each rule applies from the chosen start year (April 2030 by default). Rules that look back, such as the CBP Lookback Reform, count the Triple Lock upratings before the start as part of their history.
| Option | Rule |
|---|---|
| Triple Lock (baseline) | The highest of CPI, earnings growth and 2.5%. |
| CBP Lookback Reform | The higher of that year's CPI, or the catch-up needed to keep pension growth over the chosen window (10 years by default, ending with the current year) in line with earnings growth over the same years, or with 2.5% a year if that is higher. |
| CBP Lookback + 2.5% Floor | The CBP Lookback Reform with the Triple Lock's 2.5% guarantee kept: the highest of that year's CPI, 2.5%, or the same catch-up to earnings growth over the chosen window (10 years by default). With the annual floor in place the 2.5%-a-year comparison inside the catch-up can never bind, so the rule is simply CPI, 2.5% or the earnings catch-up, whichever is highest. Added 5 October 2026. |
| IF Cap-then-Average | From 2030, CPI only until the chosen cutoff year (2031 by default), then the average of CPI and earnings growth. |
| RF Smoothed Earnings Link | Earnings growth, holding the pension at its share of median full-time earnings when the reform starts in 2030. In a year when CPI is higher the pension rises by CPI, and stays on CPI until its share of earnings is back to that level. No 2.5% floor (Resolution Foundation, 2026). |
| IFS Smoothed Earnings Link | The same mechanism, anchored to a target share of median full-time earnings, which the IFS leaves to government at or above today's level (IFS Pensions Review, 2025). The slider sets the target from 30% to 35%. The share is tracked from 2026, so a 30% target also works off any rise in the share under the Triple Lock between 2027 and 2029. The IFS does not say how a higher target would be reached; the model assumes the Triple Lock continues until the pension first reaches it, then the smoothed link applies, returning the pension exactly to the target after each period of CPI uprating. |
| RF Smoothed Triple Lock The PM's plan from April 2030 | The pension rises by at least the higher of CPI and 2.5% every year. The model tracks an earnings path: where the pension would be had it risen with earnings every year since 2030. On that path, the pension gets the highest of CPI, earnings growth or 2.5%, like the Triple Lock. When a 2.5% or inflation-driven rise takes it above the path, it gets only the higher of CPI and 2.5% until earnings growth catches the path up, and then lands exactly back on it. So the Triple Lock's annual guarantees stay but its ratchet does not: by 2049 the pension sits about 6% above an earnings-linked pension (median across simulations, relative to an earnings link from April 2029), against about 20% under the Triple Lock (Resolution Foundation, 2026). RF does not give an exact clawback formula; this is our reading of its design. |
| Leunig 5-Year Triple Lock | CPI with a 2% floor each year, plus a catch-up every five years if cumulative earnings growth has outpaced the pension (Tim Leunig, 2023). The proposal also lets the government bring the catch-up forward when earnings are growing fast; that option is not modelled. |
| Earnings Only | Earnings growth each year. |
| CPI Only | CPI each year. |
| Double Lock: CPI or Earnings | The higher of CPI and earnings growth. |
| Double Lock: CPI or 2.5% | The higher of CPI and 2.5%. |
| Double Lock: Earnings or 2.5% | The higher of earnings growth and 2.5%. |
| 2.5% Only | A flat 2.5% every year. |
The baseline is the model's own projection of the Triple Lock, not the OBR's forecast, so savings will not match a costing scored against the OBR's Economic and Fiscal Outlook. Inflation and earnings do not respond to pension policy, and nobody changes their behaviour. The model does not include Pension Credit, whose spending would rise for some pensioners if the State Pension grew more slowly, offsetting part of the saving.
The forecasts also have four known weaknesses, which we are working on. First, inflation settles too high. Nothing anchors it to the Bank of England's 2% target: over 2032–49 it averages 2.9% a year, a level set by the 2001–26 data. This mainly raises the cash figures; the present values are deflated by each path's own inflation, so they are less affected.
Second, earnings growth is too volatile. Year-to-year variation in simulated May to July earnings growth is 2.5 percentage points, against 2.2 in the historical data. Part of this comes from the pandemic: the furlough-distorted months from March 2020 to September 2021 account for about a quarter of the unexplained variation in the earnings equation. Because the Triple Lock pays the highest of three measures, extra volatility in earnings raises its cost, and so the savings from replacing it. This works in the opposite direction to the thin-tailed inflation shocks described above, so the net effect is unclear.
Third, the ranges are too narrow. Every simulation uses the same estimated coefficients, so the 10th to 90th percentile ranges reflect uncertainty about future shocks but not about the model itself. Fourth, the data end in April 2026. The May to July 2026 earnings figure, one of the three readings for the April 2027 uprating, has since been published but is still simulated here.
Separately, past upratings are rebuilt from the latest ONS data, and earnings figures have been revised since each uprating was set. Some years therefore differ from the rise actually paid by up to 0.3 percentage points (8.4% against 8.5% in 2024, and 4.4% against 4.1% in 2025). This affects the charts of past upratings on the first page, and the rules that look back at past upratings, such as the CBP Lookback Reform.
Together with the full-rate spending base described above, these limitations set the precision of the estimates: they are a guide to the relative cost of each rule, and to the rough scale of the savings.
| Dataset | Publisher | Used for |
|---|---|---|
| CPI index, all items (D7BT) | ONS | Monthly inflation model |
| CPI 12-month rate (D7G7) | ONS | Historical upratings |
| Average weekly earnings, total pay, level (KAB9) | ONS | Monthly earnings model |
| Average weekly earnings, total pay, growth (KAC3) | ONS | Historical upratings |
| State Pension caseload, November 2025 | DWP Stat-Xplore | Starting number of pensioners by type |
| National Population Projections, 2022-based | ONS | Mortality and State Pension age inflows |
| Family Resources Survey 2024/25 | DWP, via the UK Data Service | Pensioners' taxable incomes |
| State Pension expenditure by country of residence, 2024/25 | DWP | Share paid to pensioners abroad |
| Median full-time weekly earnings (Annual Survey of Hours and Earnings) | ONS | State Pension as a share of median earnings |