The central anxiety of retirement planning is not about investment returns or tax efficiency. It is about one question: will I outlive my money? Running out of capital before running out of years is the outcome that retirement planning exists to prevent. Testing whether your plan is robust against this risk is the most important financial analysis you can do before — and during — retirement.
Rules of thumb: the 4% withdrawal rate
The most widely cited rule of thumb in retirement planning is the "4% safe withdrawal rate." The rule originates from US research in the mid-1990s (the "Trinity Study") which examined historical US market data from 1926 to 1994. The conclusion was that a retiree who withdrew 4% of their starting portfolio value in year one, and increased this amount each year for inflation, had a high probability of not running out of money over a 30-year retirement, assuming a balanced (roughly 50/50 equity/bond) portfolio.
At 4%, a portfolio of £500,000 supports £20,000 per year of withdrawals. A portfolio of £1,000,000 supports £40,000 per year. The idea is simple and memorable, which is why it has endured.
However, the 4% rule has well-documented limitations that are particularly relevant to international investors:
It is based on US historical data. US equity and bond markets over the period studied were unusually strong. Applying the same withdrawal rate to portfolios denominated in other currencies, or invested in different markets, is not straightforward.
Valuations at retirement matter. The original research found that the starting valuation of the equity market significantly affected outcomes. Retiring into a market with extended valuations — as many retirees face today — may warrant a more conservative starting withdrawal rate.
Life expectancy has increased. A 30-year planning horizon assumed in the original research was appropriate for the life expectancies of the 1990s. For a 60-year-old today, a 30+ year retirement is not unusual. Longer retirements require lower withdrawal rates to achieve the same probability of success.
The 3% rule for longer retirements
For investors with longer planning horizons — those retiring early (before 60), those with family longevity, or those simply wanting a higher margin of safety — a starting withdrawal rate of 3% provides greater resilience.
At 3%, a portfolio of £1,000,000 supports £30,000 per year. This is a more conservative starting position that provides a larger buffer against adverse market sequences and the increasing uncertainty of a very long retirement.
The difference between 3% and 4% is not merely numerical. On a £1,000,000 portfolio, it represents £10,000 per year of consumption — a meaningful lifestyle difference. The trade-off is between spending more now and maintaining greater confidence that the portfolio will last. The right balance depends on your personal circumstances, other income sources, and appetite for risk.
Sequence of returns risk
The 4% rule research drew attention to a concept that many investors underestimate: sequence of returns risk. In a portfolio subject to ongoing withdrawals, the order in which returns arrive matters enormously.
A retiree who experiences poor returns in the early years of retirement — while withdrawing a fixed percentage — is forced to sell assets at depressed prices to fund withdrawals. This permanently reduces the portfolio's ability to recover in subsequent good years. A retiree who experiences the same average returns over thirty years but in a different order — poor years at the end rather than the beginning — may end up with a substantially larger remaining portfolio.
This is one reason why holding one to two years of income in cash or near-cash at all times is prudent in retirement: it allows you to avoid selling equities in a downturn to fund living expenses, giving the portfolio time to recover.
Dynamic withdrawal strategies
The main practical improvement on the fixed percentage rule is a dynamic withdrawal strategy — one that adjusts withdrawals based on portfolio performance.
The simplest version: if the portfolio performs well, increase withdrawals slightly. If the portfolio performs poorly, reduce withdrawals by a defined percentage. Research suggests that even modest flexibility — reducing withdrawals by 10% in a bad year — significantly extends portfolio life while constraining the income reduction to a manageable level.
More sophisticated approaches use guardrails: if the portfolio rises to a defined level above plan, spending increases; if it falls to a defined level below plan, spending reduces. These strategies provide a more realistic picture of how retirement income might evolve while dramatically improving the probability that the money lasts.
Other income sources: changing the equation
The 4% rule and its variants assume that the portfolio is the sole source of retirement income. For most retirees, it is not — and the presence of other income sources fundamentally changes the withdrawal analysis.
UK State Pension. For UK nationals with sufficient qualifying years (35 for a full new State Pension), the State Pension provides an income stream that reduces the required drawdown from the investment portfolio. As of 2026, the full new State Pension is worth several thousand pounds per year. Every pound of State Pension income reduces by one pound the amount you need to draw from your portfolio each year — significantly extending portfolio life.
Note: UK nationals living in "frozen" countries do not receive annual increases to their State Pension. Check whether your country of residence is on the frozen list — see our article on this topic.
Defined benefit (final salary) pension. If you have a defined benefit pension from past employment, this pays a guaranteed income for life — typically inflation-linked or partially so. This is the gold standard of retirement income: it cannot be outlived, it does not depend on investment performance, and it reduces the portfolio withdrawal rate required to cover remaining expenses.
Rental income. If you hold investment property, rental income covers a portion of living expenses and reduces the portfolio drawdown required. However, rental income is not guaranteed — void periods, rent arrears, and property market disruptions can affect it.
Part-time work. Many retirees continue some form of paid work in the early years of retirement — not necessarily from financial necessity, but from preference. Even modest earned income in the early retirement years — the highest-risk period for sequence of returns — can significantly extend portfolio life by reducing the required withdrawal rate in vulnerable years.
Knowing your number
The most valuable output of retirement income modelling is not a specific projection — which will inevitably be wrong in its precise details — but a sense of whether the gap between what you have and what you need is manageable or requires action.
If your model shows that your portfolio comfortably supports your expected lifestyle through a long retirement with a reasonable margin of safety, you can proceed with confidence — and perhaps spend more generously in the early active years than you otherwise might.
If your model reveals a gap — that your portfolio, at a sustainable withdrawal rate, does not cover your planned lifestyle — it is far better to discover this before retirement than after. The remedies available before retirement (working longer, saving more, adjusting lifestyle expectations, considering part-time work in early retirement) are far better than the options available once you have stopped working and are depleting capital.
Our retirement calculator allows you to model your own situation — entering your capital, expected withdrawal rate, other income sources, investment return assumptions, and time horizon — to see whether you are on track.
The value of regular review
Retirement income planning is not a one-time exercise. The inputs change — investment returns, inflation, spending patterns, health, family circumstances — and the plan needs to be revisited, typically annually or after a significant life event.
A formal annual review with a financial adviser — checking portfolio performance, reassessing the withdrawal rate, adjusting for inflation, and reviewing other income expectations — is one of the most valuable uses of advisory services in retirement.
This article is for general information purposes only. Withdrawal rate analysis is illustrative and not a guarantee of any specific outcome. The value of investments can fall as well as rise. Past performance is not a guide to future returns. Individual circumstances vary significantly. Global Investments recommends seeking independent financial advice — contact us to speak with our team.
This article is for general information only and does not constitute financial, legal or tax advice. Rules, prices and regulations change; verify current requirements with a qualified adviser before acting.