The 4% Rule: Original Research and Dollar-Withdrawal Example

What the original research actually examined

William Bengen’s 1994 study, reprinted by the Journal of Financial Planning, examined historical U.S. stock and intermediate-term Treasury returns and inflation. It tested an initial withdrawal as a percentage of the starting portfolio, followed by inflation-adjusted dollar withdrawals, and considered stock/bond allocation and portfolio longevity.

Its often-cited roughly 4% starting rate survived at least 30 years in the historical cases studied under its assumptions. That is not a guarantee for future returns, every country, fees and individual taxes, or a 45-year retirement. It also does not incorporate your later Social Security start date, household shocks or ability to vary spending.

Dollar withdrawals are different from a constant percentage

Synthetic arithmetic: start with $1 million, take $40,000 in year one, and suppose inflation is 3% and then 2%. For comparison only, assume the next two beginning-of-year balances are $800,000 and $850,000; those are invented balances, not simulated returns.

Use the shorthand to frame a better question

The first policy stabilizes inflation-adjusted spending but can consume more shares after losses. The second reduces spending when balances fall, which may be unaffordable for fixed bills. Use the cash-flow target worksheet and sequence example to test what the shorthand leaves out.

How the rule works

With a $1 million portfolio, the shorthand begins with $40,000 in the first retirement year. Future withdrawals increase with inflation rather than staying at 4% of the current balance. That distinction matters: after a market decline, the planned dollar withdrawal can become a larger percentage of remaining assets.

The rule is often used to translate spending into a rough savings target. If investments must provide $60,000 in the first year, dividing by 4% suggests $1.5 million. This quick estimate is useful for orientation, but it ignores the shape of income and spending across retirement.

What a single withdrawal rate leaves out

Social Security or a pension may begin several years after retirement, reducing future withdrawals. Health insurance may be unusually expensive before Medicare. A mortgage may end, an RMD may raise taxable income, or a large home repair may occur in one year. One flat withdrawal pattern does not represent those shifts.

Taxes and fees also matter. A $40,000 withdrawal from a taxable account may not have the same tax effect as $40,000 from a traditional IRA. The amount available to spend can differ, and withdrawals can interact with other income.

Planning takeaway

Use the rule to estimate scale, then replace it with a year-by-year, after-tax cash-flow plan.

Understand what can change a starting rate

A longer retirement generally asks the portfolio to support more years. A concentrated or very conservative investment mix can behave differently from the portfolios behind historical research. High fees reduce net returns. A large legacy requirement raises the finish line. Flexible spending can provide a response that a rigid inflation-adjusted rule does not allow.

These factors do not produce one correct rate. They explain why the starting rate should be tested rather than declared safe. Run several rates through the same assumptions and compare the downside paths, not only the median ending balance.

• HorizonRetiring at 50 requires a different test from retiring at 70.
• Income timingLater Social Security or pension income can reduce the portfolio's long-term burden.
• FlexibilityA household able to trim optional spending may use a different policy from one with fixed needs.

Turn the shortcut into a withdrawal policy

A policy describes how spending changes when the plan moves outside a preferred range. You might set a base spending target, a flexible portion, and a review rule after unusually poor or strong returns. This keeps adjustments connected to the household rather than to a generic percentage.

Review the policy annually alongside Social Security, taxes, account balances, and upcoming goals. The purpose is not to recalculate life every month. It is to notice when the original plan no longer reflects reality and make a measured adjustment while options remain.