Beyond the 4% Rule: Bengen's 4.7%, Guardrails, and What Early Retirees Should Use

Bengen's 4.7% withdrawal rate does not automatically replace 4% in an early-retirement plan. It describes a particular portfolio and a 30-year horizon. Guardrails address a different question: how much could you withdraw if you agree to cut spending when your portfolio struggles?

For an early retiree, both the horizon and the cuts need scrutiny. Retiring at 45 and planning through 90 means funding 45 years. And a 19% cut to your whole budget could consume almost every dollar you consider optional. A higher starting rate is useful only if you can live with the conditions attached to it.

What changed from 4% to 4.7%

William Bengen's original study examined historical US stock and Treasury returns. A first-year withdrawal of about 4%, followed by inflation adjustments to that dollar amount, survived at least 30 years in the cases he studied.

That distinction matters: on $1 million, the first withdrawal is $40,000. With 3% inflation, the next is $41,200, regardless of the portfolio's new balance. You are maintaining purchasing power, rather than recalculating 4% of whatever remains.

Bengen later expanded the investments he modeled. In a firsthand interview explaining the revision, he attributes the increase to 4.7% to the broader asset mix. On $1 million, that is $47,000 initially, or 17.5% more than $40,000.

His SAFEMAX is the highest starting rate that survived the worst historical starting conditions under the specified assumptions. It is neither an expected return nor a guarantee about the next retirement. Changing the portfolio assumption does not also grant you a longer retirement or a spending rule with no cuts.

Why the order of returns matters

Consider an invented ten-year path for a $1 million portfolio: −15%, −10%, +5%, +20%, +15%, +10%, +8%, +12%, +6%, +9%. These are returns after inflation. Ignore taxes and fees, and withdraw $50,000 at the start of each year, before applying that year's return.

Run the same returns forward and backward:

Balance after	Losses first	Reversed order
Year 3	$663,338	$1,113,986
Year 10	$889,090	$1,115,643

Without withdrawals, both orders end at about $1,704,106. With withdrawals, the losses-first path ends roughly $227,000 behind. The return sequence changed; the set of returns did not.

The mechanism starts immediately. Withdraw $50,000, then lose 15%: $950,000 × 0.85 = $807,500. The next $50,000 withdrawal removes 6.2% of that smaller balance. Less capital remains to participate in the recovery. This is sequence risk: withdrawals make the timing of returns consequential.

This example isolates one mechanism. Inflation, portfolio allocation, fees, taxes and retirement length also affect what withdrawals a plan can support.

What guardrails ask you to give up

Jonathan Guyton and William Klinger's research uses decision rules to adjust withdrawals. Their capital-preservation and prosperity rules use 10% spending changes when the withdrawal rate moves more than 20% above or below its starting rate.

To isolate that trade, use a simplified rule on our losses-first path: start at $50,000, or 5%. Before each year's withdrawal, divide planned spending by the current balance. Above 6%, cut spending by 10%; below 4%, raise it by 10%. Otherwise leave it unchanged. Carry the resulting amount into the following year.

This is an illustration, not the full Guyton-Klinger strategy, which also has portfolio and inflation-adjustment rules and stops its capital-preservation cuts in the final 15 planned years. Our ten-year illustration applies its simplified thresholds throughout, in today's dollars.

Ten-year result	Fixed $40,000	Fixed $50,000	Simplified guardrails from $50,000
Total withdrawn	$400,000	$500,000	$419,000
Ending balance	$1,052,093	$889,090	$1,018,733
Lowest annual withdrawal	$40,000	$50,000	$40,500

The guardrail plan cuts in years 2 and 3: $50,000 × 0.9 × 0.9 = $40,500. Spending stays there through year 10. It preserves more capital than fixed $50,000 withdrawals, but most years deliver much less spending than the starting amount suggests. This path shows the exchange; it does not establish a sustainable rate or a probability of success.

Suppose essential costs consume $40,000 of that $50,000 budget. The two cuts remove $9,500 from a $10,000 discretionary allowance: 95% of optional spending. Calling yourself flexible because 20% of your budget is discretionary would miss how little room remains. Another cut would reach the essential bills.

Choose the horizon and the cut before the rate

Bengen explicitly says withdrawal rates depend on the planning horizon: 4.7% is his 30-year result, and longer retirements produce lower rates in his work. A 45-year plan needs evidence for that horizon. The first ten years of our illustration cannot supply it.

Flexibility can support a different plan, but it cannot promise comfortable spending or eliminate failure. A future path could demand deeper cuts than this example, and a historically successful plan could encounter conditions outside its sample.

Before increasing your starting rate, write down which expenses you would remove after one 10% cut, then after another. Include taxes and healthcare in the budget, and consider how long you could tolerate those reductions. If the second list is mostly unavoidable bills, choose a lower spending promise or change the plan's income, timing or costs.

The Can I FIRE Yet? Calculator lets you change the withdrawal assumption and compare the required portfolio and savings gap. It uses a steady-return projection, not these guardrails, and does not establish retirement readiness. Check which assets can actually fund withdrawals before interpreting the result. The rate becomes meaningful when you can name the spending it funds and the cuts you would accept.

This is general planning information, not personalised financial or investment advice.