Where the 4% Rule Comes From
Financial planner William Bengen published research in 1994 analysing historical US market returns from 1926 onward. He found that a retiree withdrawing 4% of their initial portfolio balance — then adjusting annually for inflation — would not have run out of money in any 30-year historical period, even those beginning just before major downturns like 1929 or 1973. The “Trinity Study” (1998) further validated this with Monte Carlo simulations.
The rule assumes a portfolio of roughly 50–60% equities and 40–50% bonds. It applies to a 30-year retirement horizon — someone retiring at 65 planning to age 95.
How It Works in Practice
Year 1: multiply your total portfolio by 0.04. That’s your withdrawal amount. If you have $800,000, that’s $32,000 in year one.
Year 2 onward: increase last year’s dollar withdrawal by inflation (CPI). If inflation is 3%, your $32,000 becomes $32,960 in year two — regardless of portfolio performance that year. The withdrawal amount is anchored to year-one dollars, not a percentage of the current balance.
| Portfolio Size | Year-1 Withdrawal (4%) | After 3% inflation (Yr 2) |
|---|---|---|
| $500,000 | $20,000/year | $20,600 |
| $1,000,000 | $40,000/year | $41,200 |
| $1,500,000 | $60,000/year | $61,800 |
| $2,000,000 | $80,000/year | $82,400 |
Limitations and When to Adjust
Longer retirements: The 4% rule was designed for 30 years. Retiring at 55 with a 40-year horizon increases sequence-of-returns risk. Many planners recommend 3–3.5% for early retirees.
Low expected returns: Bengen’s research used historical US returns that included periods of exceptional performance. With current valuations and lower expected bond yields, some researchers suggest 3.3–3.5% as more conservative for new retirees.
Flexibility matters: Rigid adherence fails in deep downturns. A “dynamic withdrawal” approach — cutting spending modestly in bad market years and spending slightly more in good years — significantly improves portfolio longevity over fixed rules.
Global Perspective
UK: The 4% rule was calibrated on US market data. UK retirees face different equity and gilt return expectations. Research suggests UK-equivalent safe withdrawal rates may be 3.5–3.7% over 30 years using a UK-weighted portfolio. State Pension (full New State Pension: £11,502/year in 2026/27) reduces the required withdrawal from personal savings significantly. MoneyHelper retirement planning at moneyhelper.org.uk.
India: India has historically higher equity returns but also higher inflation, making direct application of the 4% rule unreliable. A purchasing-power-adjusted framework — targeting real (inflation-adjusted) returns — is more appropriate. The EPF/NPS provides a partial retirement income floor. Financial planners in India often model 3–3.5% real withdrawal rates for well-diversified portfolios.
Canada: CPP and OAS reduce the required portfolio withdrawal significantly. A Canadian with maximum CPP ($1,306/month in 2026) and OAS ($713/month) has $24,228/year from government sources before drawing on savings. This dramatically reduces portfolio withdrawal pressure and may support higher personal withdrawal rates from savings. FCAC at canada.ca.