The 4% Rule, and the Case Against It

Where the rule comes from

In 1994, financial adviser William Bengen tested how much a retiree could safely withdraw from a portfolio without running out of money over 30 years, using historical US market returns going back to the 1920s. He found that an initial withdrawal of about 4%, increased each year with inflation, survived every historical 30-year window he tested. Later, the widely cited "Trinity study" reached broadly similar conclusions.

The appeal is obvious: it turns a terrifyingly open-ended question — how much is enough? — into a single number you can plan around. Flip it over and you get the famous target: to fund $40,000 of annual spending, you need roughly $1,000,000, because $40,000 is 4% of a million.

What it actually promises — and what it does not

The rule does not promise your portfolio grows, stays flat, or even survives in every imaginable future. It promises that, across the historical periods studied, a 4% inflation-adjusted withdrawal from a stock-heavy portfolio lasted at least 30 years. That is a statement about the past, in one country, over a specific horizon.

Crucially, the withdrawal amount is set in year one and then only adjusted for inflation. You do not recalculate 4% of your current balance each year — that would be a different, more conservative strategy. The original rule deliberately ignores how the market is doing, which is both its simplicity and its weakness.

The case against it

Several criticisms have gained traction. First, horizon: someone retiring at 40 might need their money to last 50 years, not 30, which pushes the safe rate down toward 3.25–3.5%. Second, starting conditions: when valuations are high and expected future returns are lower than the historical average, the comfortable cushion shrinks.

Third, and most important, is sequence-of-returns risk. A retiree who hits a severe downturn in the first few years — while withdrawing money at the same time — can permanently damage the portfolio even if the long-run average return is fine. The same average with a bad early run can fail where a good early run would have left a fortune.

More flexible alternatives

Modern approaches add flexibility the original rule lacks. "Guardrails" strategies raise or cut spending when the portfolio drifts past set thresholds, letting you spend more in good years and tighten in bad ones. Variable-percentage withdrawal takes a set percentage of the current balance each year, so spending naturally flexes with the market.

Others keep a cash buffer of two to three years of expenses so they never have to sell investments at the bottom, or use a "bond tent" that holds more bonds around the retirement date to blunt early shocks. None is magic, but each directly targets the early-downturn problem the fixed 4% rule cannot handle.

How to use it sanely

The 4% rule is at its best as a quick reality check and a way to set a savings target, not as a withdrawal plan you follow mechanically for 30 years. Multiplying your desired annual spending by 25 gives a rough finish line to aim at while you are still accumulating.

As you approach retirement, replace the rule of thumb with a plan that accounts for your actual horizon, your real spending (which often falls in later retirement), guaranteed income like pensions or social security, and your tolerance for adjusting along the way. The number is a doorway into the conversation, not the final answer.

Try the calculator

• Retirement Planner — Project your retirement savings, see your safe annual withdrawal, and find the gap to your target. Inflation-adjusted "today's money" toggle included.
• Compound Interest Calculator — See how your starting balance plus monthly contributions grow over time at a given annual rate. Includes a year-by-year breakdown of contributions vs. interest earned.