Alas, poor 4% rule. I knew it well.
The rule was born in 1994, the creation of financial advisor William Bengen, who studied historical market data back to 1926 and asked a simple question: what withdrawal rate would have survived every 30-year retirement period in stock market history? His answer was 4%. His research was grounded in decades of real market data, tested against the Great Depression, the stagflation of the 1970s, and every bear market in between. At the time, it was an extremely valuable tool. Today, however, the 4% rule is practically Elizabethan; a 30 year old rule is showing its aging utility in the area of retirement planning.
Still, for a generation of pre-retirees, that number became gospel. Pull 4% of your portfolio in year one, adjust for inflation every year after, and your money should last 30 years. Simple and defensible, the 4% rule spread through financial planning curricula, FIRE forums, and CFP exam prep like the ghost of Hamlet’s father through the corridors of Elsinore.
The ghost is still wandering those corridors. And it’s time to hear what it’s actually saying.
Act I: What the Rule Actually Was — And What It Wasn’t
Before we put it in the ground, it’s worth understanding what made it work — and what it never claimed to be.
Bengen’s 1994 paper wasn’t trying to solve retirement. It was trying to answer one specific question: what withdrawal rate would have survived every 30-year retirement period ? His answer was 4.1%. Not a universal law — a historically derived lower bound, tested against the worst historical scenarios for a specific portfolio over a specific horizon. It was popularized to 4% and stuck.
The number has genuine debate around it. Bengen himself revised his recommendation upward to 4.7% in his 2025 book A Richer Retirement, arguing his original dataset was incomplete — he hadn’t fully accounted for small-cap value stocks, which have historically outperformed large-cap equities. Morningstar’s December 2025 State of Retirement Income report, using forward-looking return assumptions, puts the appropriate starting rate for 2026 at 3.9%. The range is real: somewhere between 3.9% and 4.7% depending on your dataset and your assumptions about future returns.
But arguing about the number is the wrong argument. The 4% rule’s limitation isn’t the percentage — it’s the method. The common knowledge of this is that this is a formula you once before you retire and then the advice stops. That’s not a retirement plan, and no one expects to figure out their retirement with a set-and-forget rule. Ultimately, the 4% rule is a pretty good retirement guess. Polonius dispenses similar guidance in Hamlet, including aphorisms like “to thine own self be true.”
As usual for Polonius’ advice – much like the 4% rule in practice – his words are *kinda* helpful but ultimately incomplete.
Act II: Something Is Rotten — The Method, Not Just the Number
“Something is rotten in the state of Denmark,” Marcellus observes in Act I. What’s rotten in retirement planning doesn’t boil down to 4.7%, or 4%, or 3.9%. It’s the assumption that a single static calculation, made on the day you retire is an adequate response to 30 or 40 years of dynamic reality. People don’t spend like this.
Four specific incompleteness problems:
“We defy augury”. Hamlet rejects the idea we can predict the future. In retirement planning this is most reflected as Sequence of Returns Risk. No matter what we do, SORR is not something we can forecast. The 4% rule was derived from the worst historical sequences so far — but it assumes you’ll somehow absorb whatever sequence arrives without adjusting. You won’t. You’ll get the sequence you get, in the order it arrives, and the method gives you no mechanism to respond when markets fall hard in year two of your retirement and panic sets in.
“The time is out of joint,” Hamlet says, and a 4% flat expenditure ignores actual retirement spending patterns. Real retirement spending patterns tend to follow something closer to the retirement “smile” — higher in the active early years, lower in the slower middle years, potentially higher again in late-life due to healthcare. The 4% rule applies a flat inflation-adjusted withdrawal to a spending pattern that is anything but flat. The method doesn’t know what decade of retirement you’re in and it doesn’t adjust.
“How all occasions do inform against me, and spur my dull revenge!” Retirement planning isn’t a one-time approach – it is informed by all occasions. The inputs that drive the calculation — your portfolio value, your actual spending, your health — change every single year. Don’t mistake back-of-the-napkin math for robust retirement planning. Sure, Hamlet is descending into darkness here with “dull revenge”, but all occasions should be considered here and provide course-correcting information as you go.
All occasions should inform against you and spur your smart retirement.
“There’s a divinity that shapes our ends, rough-hew them how we will.” One of the most frustrating aspects of retirement planning is coming up with your personal time horizon. How long will you live before you shuffle off this mortal coil? No one knows, but the 4% rule assumes 30 years. No more and no less. There’s a real longevity risk associated with this approach as we “rough-hew” them with a 30 year assumption. A couple retiring at 60 today may now need income for 35 to 40 years. Over a 40-year horizon, a 4% withdrawal rate carries a historically estimated failure rate somewhere between 3% and 13%, depending on portfolio allocation and methodology — meaningfully worse than the 30-year window the rule was built for. The method wasn’t designed for that horizon and doesn’t adapt when you live longer – or even shorter – than it assumed.
A method that doesn’t update when its inputs change isn’t a plan. It’s a snapshot you’re mistaking for the full play.
Act III: The Lady Doth Protest Too Much
The FIRE and Retirement planning community’s response to these critiques has largely been to defend the 4% rule while hedging around the edges. Honestly, this feels more like a ‘loss leader’ mentality. The industry grudgingly acknowledges the value of the 4% rule as something that seems to work as a rough estimate while insisting that it’s more complex and you need to talk to a financial planner to get in-depth answers.
“The lady doth protest too much, methinks,” in Hamlet, Gertrude speaks of someone whose excessive declarations have become their own evidence of insincerity. The continued insistence of the value of the 4% carries that same quality. The more emphatically it’s defended, the less convincing the defense becomes.
Morningstar says 3.9%. Bengen says 4.7%. The FIRE community argues for 3.3% for longer retirements…! The rule’s defenders can’t agree on what the correct number is — which suggests the number itself may be the wrong unit of analysis. The debate about the percentage is a distraction from the deeper problem: a static method applied to a dynamic reality will always require defenders, because it will always be wrong for someone.
The 4% rule doesn’t need defenders protesting on its behalf. It needs a successor. We don’t need to hearken back to a rule that does a passing job but is full of caveats. We need robust answers that get us to our retirement truth — not old rules that only seem to.
“Seems, madam? Nay, it is. I know not ‘seems.'”
Act IV: What the Ghost Tells Us
King Hamlet’s ghost isn’t just a horror for Hamlet to contend with — he’s a messenger. He delivers the information Prince Hamlet needs to act differently. The ghost of the 4% rule serves the same purpose. The message isn’t “withdraw exactly 4% plus inflation.” It’s that sustainable withdrawal rates are calculable, that the math matters, and that you need a method responsive enough to use that math as your situation actually unfolds.
Monte Carlo — a genuine upgrade
The Monte Carlo simulation is a significant improvement over the static method of the 4% rule.
Where the 4% rule runs one calculation once, Monte Carlo runs thousands of simulated futures — different sequences of market returns, different inflation paths — and shows you a probability distribution of outcomes. It tells you not just whether the math works on average, but how often it fails and under what conditions. some of the more sophisticated calculators apply variations on historical sequencing or parametric methods.
The specific advantages over the 4% rule are real: Monte Carlo accounts for sequence of returns risk explicitly rather than assuming a historical worst case. It incorporates your actual asset allocation rather than a generic portfolio. It can model variable spending across retirement phases. And critically, you can rerun it every year as your actual situation diverges from what you assumed at retirement. That’s not a static snapshot. That’s a living probability estimate that updates as your inputs change. Re-running your 4% math every year would work, but it would be much slower in telling you a likelihood of success over time that a Monte Carlo simulation would highlight earlier.
But Monte Carlo has its own limitation: it gives you a probability of success without telling you what to do when that probability starts to move. It’s a diagnostic tool, not a decision framework. You can know you have a 73% probability of success without knowing whether to spend less, work longer, or adjust your asset allocation. The calculation is dynamic. The response to it still has to come from somewhere else.
Other frameworks that go further
The three methods that follow Monte Carlo in the direction of dynamic planning each address a different dimension of that response:
One such approach is the Guardrails approach — developed by Jonathan Guyton and William Klinger — build the response directly into the spending rule. Set upper and lower bounds on your withdrawal rate. When your portfolio grows substantially, you can spend more. When it falls, you pull back. The method adjusts automatically to what’s actually happening, rather than waiting for you to rerun a calculation and decide what to do with the result.
Ken Steiner’s actuarial approach goes further still — rather than modeling the portfolio, it models the full household balance sheet. Every year you compare the present value of everything you’ll spend against the present value of everything you have, calculate your funded status, and set this year’s spending budget based on where you actually stand. It’s Hamlet updating his understanding of the situation each time new information arrives, rather than executing a plan formed before he knew the full truth.
ARVA — Stefan Sharkansky covers the Annually Recalculated Virtual Annuity. This builds the dynamism into the portfolio architecture itself. A TIPS ladder funds your essential spending floor; a stock index fund covers everything above it; annual recalculation keeps the withdrawal aligned with current market values and remaining life expectancy. The method doesn’t just respond to what happens — it’s structured so that the response is automatic.
The 4% rule gave us the insight that sustainable withdrawal rates are calculable. These more robust frameworks give us methods worthy of the 30 or 40 years that follow.
Stabbing the curtain
Last note on any framework: every method requires good inputs. Bad inputs can lead to disaster, like Hamlet stabbing the curtain. “Thou wretched, rash, intruding fool, farewell!”. That one moment of bad decision making based on bad information moved much of the plot of the play. The beauty of using a good framework with good inputs every year is that you can update that information and prevent 30 years of sorrow based on a momentary bad decision.
Act V: To Retire, or not to Retire
“To be or not to be” is Hamlet’s most famous question. The 4% rule helps us answer the retirement question at the same basic level, viscerally: To retire or not to retire? It’s grossly incomplete. We don’t need to extemporize iambic pentameter to understand this.
As we approach retirement, Hamlet’s soliloquy resonates:
“To be retire, or not to be retire: that is the question:
Whether ’tis nobler in the mind to suffer
The slings and arrows of outrageous fortune managers…”
I don’t think even the genius of the Bard of Avon really recognized how a bad manager might drive behavior…
The simplicity of the 4% rule allows us to pre-assess at some level what the chances are for future slings and arrows, but ultimately we’re not emo princes in Denmark in the late middle ages. We’re adults and we should have moved past whether we should be existing at all. While the 4% rule answers a primitive question, it does not provide the full solution.
The right solution requires that we use a more sophisticated approach. Given what we know about our actual situation — our personal risk tolerance for sequence risk, our planning horizon, our spending variability, our income sources, and even the composition of our portfolio — what are our expenses for each year and therefore our our sustainable withdrawal rate and funding sources for each year, and how do we keep it updated as reality diverges from assumptions?
Bengen gave us a starting point. Guardrails, actuarial methods, and ARVA each offer ways to make the answer more dynamic rather than static. What they share is a recognition that the number matters less than the method — and that the method needs to be a living changeable thing, not an echo of a ghost.
The 4% rule isn’t dead in the sense that the underlying insight — that sustainable withdrawal rates are calculable and worth knowing — is as valid as it ever was. It’s dead in the sense that the specific number, applied rigidly without adjustment, is a ghost of a calculation made for a world that has, like ye olde English itself, evolved in its ability to provide more robust tools for retirement planning.
Listen to what the ghost is telling you and use more sophisticated approaches in your planning.
Run your own numbers — 2,000 Monte Carlo simulations, your actual spending, your actual timeline, free — at the Retirement Probability Calculator here on this page, or at the other links above. See what your probability of success looks like at 4%, at 3.9%, and at 3.5% or via another approach. That’s the rigor the 4% rule conversation was always trying to start.
All we can do is plan and prepare to be ready for our retirement: “If it be now, ’tis not to come; if it be not to come, it will be now; if it be not now, yet it will come.
The readiness is all.”