Sustainable Withdrawal Rates: The 4% Rule, Its Limitations, and What to Use Instead

The Origin of the 4% Rule

In 1994, financial planner William Bengen published a study that became one of the most influential papers in retirement planning. Using historical US stock and bond market data stretching back to 1926, Bengen examined what would have happened to a retiree's portfolio under different withdrawal rates across every 30-year retirement window in the dataset.

His finding was that a withdrawal rate of 4% in the first year of retirement — adjusted upward each subsequent year by the actual inflation rate — would have sustained a balanced portfolio (roughly 60% equities, 40% bonds) through every 30-year period in the historical record, including the Great Depression, the oil crises of the 1970s, and other severe market downturns. The "4% rule" was born.

Subsequent research by the "Trinity Study" in 1998, and numerous updates since, broadly confirmed Bengen's finding with some refinements: 4% produced a high historical success rate for 30-year retirements, though not 100% success in all scenarios.

The rule became a shorthand for retirement income planning, particularly in the United States. It is referenced in countless financial planning conversations, often as if it were a universal and reliable guide. The reality is considerably more nuanced.

The Assumptions Behind the Rule

To use the 4% rule intelligently — and to understand where it may fail — it is essential to understand the assumptions baked into the original analysis.

US market data. The rule is based entirely on the historical performance of US equity and bond markets. The United States had an exceptionally strong equity market over most of the twentieth century, in part reflecting the extraordinary growth of the US economy during that period. Historical UK equity returns, while also positive over the long term, have not consistently matched US returns. Applying US-derived withdrawal rates to UK or internationally diversified portfolios introduces a systematic optimism bias.

A 30-year retirement. The analysis is framed around a 30-year retirement — broadly, retiring at 65 and living to 95. For clients who retire at 55 or 60, or who have family histories of exceptional longevity, a 35 or 40-year horizon is more appropriate. The 4% rule becomes substantially less reliable as the time horizon extends. Research suggests a 3.0–3.5% rate is more defensible for 35-40 year retirements even using US data.

No fees. The original analysis assumed no investment management fees, no platform charges, and no adviser costs. In practice, a drawdown portfolio incurs fees at every level. Research consistently shows that each 1% of annual fees reduces the sustainable withdrawal rate by roughly 0.5 percentage points.

Inflation-adjusted fixed withdrawals. The rule assumes you take a fixed amount in real terms every year, adjusted upward with inflation. This is not how most people actually spend in retirement — spending tends to be higher in the early active years and lower later (though healthcare costs can rise substantially in very late retirement). A spending pattern that front-loads income needs early will exhaust the portfolio faster than the rule suggests.

A specific asset allocation. The rule is calibrated to a roughly 60/40 equity/bond portfolio. Higher equity allocations perform better over long periods but introduce greater sequencing risk (see our dedicated guide); lower equity allocations reduce long-term returns and may not sustain a 4% withdrawal rate over an extended period in a low-return environment.

Why the 4% Rule May Not Apply to International Investors

For our clients — many of whom live outside the UK, hold multiple currencies, receive income in pounds and spend in euros, dirhams, bahts, or other currencies — additional factors further complicate the application of a US-derived rule.

Currency risk. A UK pensioner living in Spain drawing a GBP pension and spending in euros faces exchange rate risk on every withdrawal. If sterling weakens against the euro, the real purchasing power of GBP withdrawals falls even if the nominal amount is unchanged. A sustainable withdrawal rate in GBP terms may not translate to a sustainable real spending level in the currency of expenditure.

Different inflation experiences. Local inflation in the country of residence may differ significantly from UK CPI. Healthcare cost inflation, which is often higher than general inflation and particularly relevant for retirees abroad who rely on private health insurance, may exceed the headline rate substantially.

Different tax treatment. Tax treatment of drawdown income varies by jurisdiction. A client in a country with no income tax (such as the UAE) effectively keeps more of each withdrawal than a client in a country with significant income taxes on pension income. Tax efficiency can meaningfully affect the real withdrawal rate.

Updated Research: What Is Sustainable in the Current Environment?

Several researchers have revisited the 4% rule in the context of the post-2008 interest rate environment and the structurally different forward-return expectations that some analysts apply to developed market equities.

Academic researchers Michael Finke, Wade Pfau, and David Blanchett published influential research suggesting that under lower expected future returns — reflecting both lower bond yields and potentially lower equity risk premiums than the US historical average — safe withdrawal rates for 30-year retirements might be closer to 2.5–3.0%. Their analysis prompted considerable debate.

Most current practitioner consensus sits somewhere between the original 4% and these more conservative estimates. For UK investors, with a 30-year horizon, a broadly diversified global portfolio, and a fee structure of around 1–1.5% total annual charges, a starting rate of 3.0–3.5% is commonly cited as a more appropriate conservative starting point.

For 35-40 year retirements, 2.5–3.0% is often suggested as the conservative planning rate, rising to 3.5–4.0% if the client has significant income flexibility (can reduce withdrawals in bad years) or a strong guaranteed income floor.

Dynamic Withdrawal Strategies: What to Use Instead

The core problem with a fixed withdrawal rule is that it does not adapt to changing market conditions. A portfolio that has grown strongly in years one to five can sustain higher withdrawals than one that has suffered significant losses. Using a fixed rule ignores this information.

Dynamic withdrawal strategies address this by adjusting the income taken each year in response to portfolio performance. Several approaches are in common use.

Fixed Percentage of Current Portfolio

Rather than withdrawing a fixed amount adjusted for inflation, you withdraw a fixed percentage of the portfolio's current value each year. If the portfolio has grown, withdrawals increase automatically; if it has fallen, withdrawals decrease.

This approach guarantees the portfolio never runs out — you are always taking a fraction of what remains. The trade-off is income volatility: withdrawals fluctuate with markets, which may be uncomfortable for clients with fixed essential expenses. It works best when a guaranteed income floor covers essentials and the drawdown is for discretionary spending.

Floor and Ceiling (Guardrail) Strategy

The guardrail approach sets boundaries around a target withdrawal rate. For example: withdraw 4% in year one, and adjust each year by inflation — but if the withdrawal rate as a percentage of the current portfolio rises above 5.5% (the ceiling), cut withdrawals back; if it falls below 3% (the floor), increase withdrawals. This prevents both the income collapse of a purely fixed-percentage approach and the portfolio exhaustion of a purely fixed-amount approach.

Required Minimum Distribution Method

Popular in the United States for tax reasons, this approach divides the remaining portfolio each year by the remaining expected lifetime (from actuarial tables) and takes that amount as the withdrawal. It naturally reduces withdrawals as the portfolio shrinks and adjusts to longevity expectations. It is not directly applicable in the UK tax context but illustrates the logic of actuarially-informed drawdown.

The Impact of the State Pension and Other Guaranteed Income

One of the most significant factors affecting the required drawdown rate — and one that is often underweighted in discussions of the 4% rule — is the presence of guaranteed income from other sources.

The full new State Pension is currently around £12,548 per year. A client who needs £30,000 per year in total and receives £12,548 in State Pension needs their drawdown pot to generate only around £17,450 per year — a 4.4% withdrawal rate on a £400,000 pot, which is quite different from the 7.5% rate that would be required with no State Pension at all.

For clients who retire before State Pension age — currently 66, rising to 67 — the planning exercise involves two phases: a higher drawdown rate from retirement to State Pension age, then a lower rate thereafter. We model both phases explicitly, ensuring clients are not misled by a single headline withdrawal rate.

Similarly, clients with defined benefit pension income have a guaranteed income floor that substantially reduces the dependence on the drawdown portfolio. For a client whose DB pension plus State Pension covers all essential expenses, the drawdown pot can be managed at a much lower withdrawal rate — or even preserved almost entirely for estate planning purposes.

How Often to Review

A sustainable withdrawal rate is not a figure set once at retirement and left unchanged for thirty years. It is a planning assumption that should be reviewed at least annually against:

The current portfolio value and performance since last review. Whether the withdrawal rate as a percentage of current portfolio value has moved outside an acceptable range. Changes in income needs — major planned expenditures, changes in lifestyle, reduction in travel as clients age. Changes in tax position or guaranteed income (particularly State Pension becoming payable, or a DB pension commencing). Changes in health or longevity expectations.

We recommend detailed drawdown reviews at least annually for all our drawdown clients, with interim reviews triggered by significant market movements or changes in personal circumstances.

Our Approach to Sustainable Withdrawal Rates

At Global Investments, we do not prescribe a single withdrawal rate guideline for our clients. The 4% rule is a useful starting point for conversation, but it is not a planning tool.

Instead, we build a bespoke financial model for each client, incorporating their specific pot size and asset allocation, their full income picture including State Pension and DB pensions, their planned spending trajectory across retirement, their health and longevity expectations, their estate planning objectives, their tax position in their country of residence, and their attitude to income variability. We stress-test this model against a range of market scenarios, including sequences of early poor returns that specifically test sequencing risk, and we present clients with a clear picture of the range of outcomes they face under different assumptions.

This rigorous, client-specific approach is substantially more useful than applying a universal rule — because the circumstances that determine whether 3.5% or 4.5% is appropriate vary enormously between clients.

How Global Investments Can Help

Whether you are planning for retirement, reviewing an existing drawdown arrangement, or questioning whether your current withdrawal rate is sustainable, our pensions team brings together actuarial modelling, investment expertise, and cross-border tax planning to give you a robust and personalised answer. We do not deal in rules of thumb when our clients' long-term financial security is at stake.

If you would like a sustainable withdrawal rate review for your drawdown plan — including stress-testing against poor early-retirement markets and modelling the impact of State Pension and other guaranteed income — please contact our team.

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Investment returns, inflation, and tax rules are all uncertain. Past performance of any market or strategy does not guarantee future results. Investments can fall as well as rise and you may get back less than you invest. The information in this guide reflects the position as of June 2026. Withdrawal rate figures are illustrative and do not constitute a guaranteed outcome. This guide is for information purposes only and does not constitute regulated financial advice. Please seek advice from a qualified pension adviser.