Sequence of Returns Risk: The Formula That Shows What a Bad First Year Really Costs
Two people retire with the exact same $1,000,000 portfolio and earn the exact same 7.9% annualized return over 25 years. One ends with $4.5 million. The other runs out of money in year 18. Nothing separates them except the order the returns arrived in — and that gap is what sequence of returns risk actually means.
It is the single most under-modeled variable in most DIY retirement plans, because the standard retirement calculator asks for one average return and quietly assumes you’ll get it evenly. You won’t. This post gives you the one-line formula that converts a bad first year into the number that actually matters — your effective withdrawal rate — plus four scenarios showing what different first years do to a 4% plan, and the four levers that measurably shrink the risk.
The quick answer: one formula that measures your sequence of returns risk
You don’t need a Monte Carlo engine to see the problem. You need two lines of arithmetic.
Step 1 — Balance after year one:
(Starting balance − Year 1 withdrawal) × (1 + Year 1 return)
Step 2 — Your effective withdrawal rate going into year two:
Year 2 withdrawal ÷ Balance after year one
Run it on a $1,000,000 portfolio with a 4% initial withdrawal ($40,000), inflation-adjusted at 2.5% so year two’s withdrawal is $41,000:
| Year 1 market return | Balance entering year 2 | Year 2 withdrawal | Effective withdrawal rate |
|---|---|---|---|
| +15% | $1,104,000 | $41,000 | 3.71% |
| 0% | $960,000 | $41,000 | 4.27% |
| −20% | $768,000 | $41,000 | 5.34% |
| −30% | $672,000 | $41,000 | 6.10% |
| −37% (2008) | $604,800 | $41,000 | 6.78% |
That last column is the whole argument. You did not change your spending. You did not change your allocation. But a single −30% year silently converted your carefully researched 4% plan into a 6.1% plan — and no credible study has ever found a 6.1% inflation-adjusted withdrawal rate to be sustainable over 30 years. Morningstar’s 2025 State of Retirement Income research put the highest safe starting rate for stable, inflation-adjusted spending at 3.9% for a 30-year horizon at a 90% success threshold.
There’s a second, uglier number hiding in that row. To get back from $672,000 to your original $1,000,000, the market has to deliver a 48.8% gain. That’s not a rebound. That’s a bull market.
Why sequence of returns risk only exists once you start withdrawing
Here’s the part that catches people off guard: during accumulation, order doesn’t matter at all.
Take a 25-year sequence of annual returns averaging 8.44% arithmetically and 7.90% annualized. Sort it worst-year-first. Then sort it best-year-first. With no contributions and no withdrawals, a $1,000,000 portfolio ends at exactly $6,697,487 either way. Multiplication is commutative. The order is irrelevant.
Now add a $40,000 withdrawal in year one, growing 2.5% a year for inflation, and run the identical returns again:
| Return ordering | Balance, year 5 | Balance, year 10 | Balance, year 25 |
|---|---|---|---|
| Bad years front-loaded | $455,200 | $300,160 | $0 (depleted yr 18) |
| Mixed / realistic order | $527,787 | $469,465 | $418,222 |
| Good years front-loaded | $2,179,477 | $4,021,673 | $4,509,263 |
Same 25 returns. Same 7.90% annualized. A $4.5 million spread, and one outright failure.
The mechanism is unglamorous: when you sell shares into a down market to fund living expenses, you permanently retire those shares from the portfolio. They aren’t there to participate in the recovery. A 30% drawdown you simply ride out is a paper loss. A 30% drawdown you withdraw through is a realized, irreversible reduction in share count. That’s why the danger is concentrated in the years right around your retirement date — research by Michael Kitces and Wade Pfau on rising equity glidepaths makes exactly this point, and it’s the reason the first decade of withdrawals carries far more weight in plan outcomes than the last decade does.
Four scenarios: what the history actually looks like
These aren’t hypotheticals. The historical record has run this experiment on real retirees.
Scenario 1 — The 1966 retiree
William Bengen’s 1994 Journal of Financial Planning study ran a 50/50 stock-bond portfolio through every rolling 30-year period from 1926 forward and found the worst starting year was 1966, with a maximum sustainable initial withdrawal of 4.15%. That’s where the “4% rule” comes from — it is not an average outcome, it’s the survivor of the single worst sequence in the sample. The 1966 cohort walked into stagflation: a nominal market that went nowhere for roughly 16 years while inflation peaked in the double digits.
Scenario 2 — The 1982 retiree
Retire 16 years later, same portfolio, same 4% rule, and you step directly into one of the longest bull markets in U.S. history. Same strategy, same asset mix, wildly different life. The retiree did nothing smarter. They were born earlier or later.
Scenario 3 — The 2000 retiree
The S&P 500 delivered an annualized total return of roughly −0.95% from year-end 1999 through year-end 2009 with dividends reinvested — only the second negative-return decade on record, alongside the 1930s. Anyone who retired in January 2000 spent their entire first decade of withdrawals selling into a flat-to-down market: a ~49% drawdown in 2000–2002, then a ~37% single-year loss in 2008.
Scenario 4 — The 2009 retiree
Retire at the March 2009 bottom and your first decade of withdrawals came out of one of the strongest equity runs in modern history. Your portfolio grew faster than you could spend it.
Four retirees. One strategy. Four completely different outcomes, driven by a variable none of them controlled. This is why the honest version of the 4% safe withdrawal rate debate is less about finding the “right” number and more about building a plan that survives being wrong about it.
Want to stress-test your own retirement date against a bad first decade?
Four levers that reduce sequence of returns risk
You can’t control the sequence. You can control how much of your spending has to come out of equities during a drawdown. That’s the entire game, and there are four practical ways to play it.
1. Flexible spending — the highest-leverage move
Look back at the −30% row: the effective rate was 6.10%. Cut your withdrawal by 10% that year and it drops to 5.49%. Cut by 20% and it drops to 4.88%. A temporary $8,200 spending reduction does more for plan survival than almost any portfolio tweak available to you.
Vanguard formalized this as its “dynamic spending” rule: set a ceiling of +5% and a floor of −2.5% on year-over-year spending changes, so you participate in good years and trim in bad ones without swinging wildly. Vanguard’s research found that specific ceiling-floor pair produced an 85% portfolio survival rate over a 35-year horizon — better odds than a rigid inflation-adjusted 4% over the same period.
2. A cash and short-bond buffer sized in years, not dollars
Two to three years of spending held in cash and short-duration bonds means a bad first year doesn’t force equity sales at all. This is the “bond tent” idea Kitces describes: raise your bond allocation in the years immediately approaching retirement, then let equity exposure drift back up once the danger zone has passed. The protection is concentrated exactly where the risk is.
The buffer costs you something in expected return — that’s real. But it’s insurance priced in basis points against a risk measured in whole portfolios.
3. Disciplined rebalancing, which forces you to sell the right asset
Rebalancing is the mechanical version of “sell what’s up, buy what’s down.” In a 30% equity drawdown, a rebalanced portfolio funds withdrawals from the bond sleeve and buys equities at depressed prices, which is precisely the behavior sequence risk punishes you for not doing. Our walkthrough of how to rebalance a three-fund portfolio covers the mechanics, and if you’re still building the portfolio itself, the three-fund portfolio for beginners is the simplest structure that makes rebalancing trivial.
4. Where you hold each asset changes what you’re forced to sell
Withdrawal order and account location interact. If your bonds sit in a traditional IRA and your equities sit in taxable, a down year gives you the option to spend from the bond side without a large tax bill. Getting asset location right relative to asset allocation won’t change your returns, but it widens the set of assets you can sell without a penalty — and optionality is exactly what you need in the danger zone.
One more structural lever, if you’re planning an early exit: shortening the withdrawal horizon isn’t an option, but lengthening the accumulation runway is. Our breakdown of how much you need to retire at 55 walks through why a 40-year horizon demands a materially lower starting withdrawal rate than a 30-year one.
What I found when I ran this on my own numbers
I’m a software engineer, not an advisor, and I run my own money — index funds, tax-advantaged accounts first, no one taking a percentage off the top. Behavioral economics is a hobby of mine, so I’ll admit the appeal here was partly that this is a problem you can solve with a spreadsheet and a loop, which is my favorite kind of problem.
What surprised me was how badly my mental model had been calibrated by calculators. I’d been feeding a single average return into projection tools for years and reading the output as a forecast. The first time I wrote the loop myself and reordered the same return series, the accumulation result didn’t move a dollar and the withdrawal result moved by seven figures. That reframed the whole thing: the number I’d been optimizing — expected return — was close to irrelevant next to a variable I’d never modeled at all.
The practical change was small and unglamorous. I didn’t overhaul my allocation. I wrote down, in advance, the specific spending cuts I’d make at a −20% and a −30% portfolio level, because I know from watching my own behavior that decisions made during a drawdown are worse than decisions made before one. That’s the whole intervention. It cost nothing and it’s the part I’d defend hardest.
Frequently asked questions
Does sequence of returns risk affect me if I’m still saving and decades from retirement?
Not in the same way. During pure accumulation with no withdrawals, the order of returns has no effect on your ending balance — the math is commutative, and identical return sets produce identical results regardless of ordering. Sequence risk becomes real once cash flows out of the portfolio, so it matters most in roughly the five years before and ten years after your retirement date. If you’re contributing regularly, a bad early sequence actually helps you, because you’re buying shares cheaply.
How large should a cash buffer be to protect against sequence of returns risk?
The common range is two to three years of spending in cash and short-duration bonds, sized so you can fund living expenses through a typical drawdown without selling equities. The trade-off is explicit: holding two years of spending in cash lowers your expected long-run return, which is why some researchers prefer a bond tent that peaks near the retirement date and declines afterward rather than a permanent cash allocation. Neither is free, and both are cheaper than depleting a portfolio in year 18.
Is the 4% rule still valid given sequence risk?
The 4% rule already accounts for sequence risk — that’s what it was built to do. Bengen derived 4.15% from the single worst historical starting year rather than from an average. The live debate isn’t whether sequence risk breaks the rule but whether today’s starting conditions are worse than 1966’s. Morningstar’s 2025 research landed at 3.9% for rigid inflation-adjusted spending over 30 years, and near 6% for retirees willing to accept year-to-year spending variability. The gap between those two numbers is the value of flexibility.
Photo by Maxim Hopman on
Unsplash
