Hundred SummersWould your retirement have survived 1929?
Averages lie about retirement: what breaks a plan is not the average return but the order the returns arrive in. This page replays your pot and spending through every complete market window since 1928 (the 1929 crash, the 1937 relapse, the 1966–81 inflation grind, the 1973 oil shock, the 2000s lost decade), each one a full UK simulation with income tax and the State Pension. Watch each history unfold, year by year. Your figures never leave your browser.
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Worked example
Computed when this page was built by the same engine that runs the calculator above, so the figures below and the live tool can never disagree. Change any input above to see your own.
| Inputs | |
|---|---|
| Retire at | 65 |
| Pot | £500,000 |
| Spending a year (today's money) | £20,000 |
| Growth assumption | 5.0% |
| Include State Pension | Yes |
| Plan to | 95 |
| Results | |
|---|---|
| Historical windows replayed | 66 (31-year retirements starting each year) |
| Survived | 66 of 66 |
| Failed | 0 |
The next question
Does the whole plan hold up, year by year? →
Only the whole picture answers that: the full Hundred Summers plan connects your pay, pensions, savings, property, tax and spending year by year, and stress-tests them across 500 simulated market histories.
Read the guides
- The 4% rule: what it misses for UK retirees →Where the famous retirement withdrawal rule comes from, why its US assumptions travel badly to the UK, and what a real projection tests instead: tax, the State Pension, and the market sequences that actually broke retirements.
- Sequence-of-returns risk, shown with real market history →Two retirees earn the same average return and one runs out of money: why the order of returns dominates retirement outcomes, which historical cohorts it broke, and how to test a plan against it honestly.
- Inflation: the assumption everything rests on →What 2.5% a year does to money over a retirement, what UK prices actually did since 1988 on the ONS index, why every figure in a Hundred Summers plan is in today's money, and how the plan is stress-tested against inflation that does not behave.
Why 1966 scares planners more than 1929
The Great Crash is the famous catastrophe, but a retirement starting in 1929 usually survived: prices fell alongside markets, so withdrawals shrank too, and the recovery, when it came, was ferocious. The start that broke retirements was 1966: returns that looked merely mediocre, ground to dust by fifteen years of inflation that forced withdrawals up while portfolios stood still. It's the window that gave the 4% rule its number, the worst case the rule was reverse-engineered to survive, and the reason any honest test replays inflation, not just returns.
That is what this page does differently from a compound-interest chart: each replayed era carries its own inflation into your spending, your tax bands and your State Pension, through the same simulation the Hundred Summers app's stress test runs. One caveat stated plainly: ninety-six years of history give one draw from reality, not a probability; the app pairs this backtest with thousands of simulated futures for exactly that reason. Related: the sequence-of-returns guide, the personal SWR calculator and the 4% rule guide.