Sequence of Returns Risk: The Retirement Math Problem

A working professional saving for retirement mostly cares about the average return they earn over their career. A retiree drawing down those same assets cares about something different: the order in which those returns arrive. Two portfolios that earn identical average annual returns over thirty years can end with radically different outcomes if one starts with three bad years and the other starts with three good ones.

This is sequence-of-returns risk. It is the single most important concept most pre-retirees have never heard of, and it is the reason the 4% rule is more fragile than it appears in the backtests. This piece walks through the math with a worked example, explains why the first ten years of retirement carry outsized weight, and covers the three mainstream strategies for reducing the exposure.

Why the average is not enough

Consider two hypothetical retirees, each starting with a $1,000,000 portfolio at age 65. Both withdraw $40,000 in year one (the classic 4% initial withdrawal rate from William Bengen’s 1994 study), and both increase their withdrawals by 3% each year for inflation. Both earn an average annual return of 5% over thirty years. The only difference is the order in which those returns arrive.

Retiree A experiences three bad years at the start: -15%, -10%, -5%. Then returns average 7% for the remaining twenty-seven years, bringing the full-period mean to 5%.

Retiree B experiences the same returns in reverse: strong early years averaging 7%, followed by three late-retirement losses of -15%, -10%, -5%. Full-period mean, 5%.

The math runs as follows. Retiree A starts with $1,000,000, withdraws $40,000 at the start of year one, then loses 15% on the remaining $960,000:

Year 1 ending value = ($1,000,000 − $40,000) × (1 − 0.15) = $816,000

Year 2: withdraws $41,200 (3% inflation), then loses 10% on the balance:

Year 2 ending value = ($816,000 − $41,200) × (1 − 0.10) = $697,320

Year 3: withdraws $42,436, then loses 5%:

Year 3 ending value = ($697,320 − $42,436) × (1 − 0.05) = $622,140

Retiree A has three years of withdrawals consumed ($123,636 total) and a portfolio that has fallen 38% from its starting value. The combination of forced selling at depressed prices and ongoing withdrawals has reduced the capital base that will have to compound at 7% to carry the remaining twenty-seven years. Even with subsequent strong returns, the drawdown that started the retirement cannot be fully made up because the compounding is being done on a smaller base.

Retiree B, by contrast, starts with three 7% years and normal withdrawals. After three years of gains against modest withdrawals, the portfolio has grown meaningfully. When the three bad years arrive at the end of retirement (years 28, 29, 30), the damage is limited because the withdrawals have already been taken from thirty years of assets.

Running the full thirty-year simulation with these inputs produces radically different outcomes. Retiree A’s portfolio is exhausted or nearly exhausted. Retiree B’s portfolio finishes with meaningful remaining capital. Same mean return, same withdrawal schedule, wildly different results.

Why the early years matter so much

The mathematical reason is straightforward. A retiree selling assets to fund withdrawals during a drawdown locks in losses that can never be recovered because the capital is no longer in the market to participate in the eventual recovery. The academic term for this effect is “negative dollar-cost averaging.” It is the inverse of the accumulator’s advantage.

During accumulation, an investor adding money in a drawdown buys more shares at lower prices and benefits when prices recover. During decumulation, a retiree selling in a drawdown does the opposite: sells more shares at lower prices and owns fewer shares when the recovery arrives.

Research by Michael Kitces and Wade Pfau has consistently shown that the first ten years of retirement carry disproportionate weight in determining whether a portfolio lasts. This period is often called the “retirement red zone.” Poor returns during these years can reduce the probability of portfolio survival by fifty percent or more, even if subsequent returns are strong.

Real historical examples

Pick any two retirement start dates in modern US history and the math becomes concrete. A retiree who began drawing down a 60/40 portfolio in January 1966 experienced the stagflation of the 1970s in the early years of retirement. Equities struggled, inflation eroded real spending power, and Treasuries offered small protection. The standard 4% rule with annual inflation adjustments failed for this cohort over the standard thirty-year horizon in most simulations.

By contrast, a retiree who began drawing down in January 1982 caught the start of the greatest bull market in US history. By the late 1980s the portfolio had grown substantially while withdrawals remained modest. When the 2000-2002 drawdown arrived, it hit a portfolio that had already survived twenty years and could absorb the hit. This cohort finished retirement with significantly more wealth than they started with in most simulations.

The Bengen 4% rule was calibrated to survive the worst such historical case. That is the entire point of the “4%” figure: it is not an expected rate, it is the rate that would have worked for the worst historical starting year on record. A retiree beginning in the best starting year could have withdrawn much more. A retiree beginning in the worst year could withdraw only 4%. The rule is built on tail risk.

What updated research says about the 4% rule

The 4% rule has come under pressure in recent research. Morningstar’s annual Safe Withdrawal Rate study has argued that current equity valuations and bond yields together produce a different tradeoff than the post-1926 historical average. Recent versions of the study have suggested safe initial withdrawal rates in the 3.7% to 4.0% range depending on portfolio composition and retirement horizon.

Wade Pfau’s research has made similar points, with some analyses suggesting that a starting withdrawal rate as low as 3.3% may be appropriate for a very conservative plan calibrated to current market conditions. Other researchers push back and argue the 4% rule still holds because the historical worst case (1966) was already severe.

This debate is live and unresolved. For planning purposes, the useful takeaway is not a single number but a range: initial withdrawal rates in the 3.3% to 4.0% band are defensible under current research, and the right choice within that band depends on the specific portfolio, the retiree’s flexibility to cut spending in bad years, and the presence of other income sources like Social Security.

Three mitigation strategies

Three mainstream strategies exist for reducing sequence risk. None is free. All involve accepting some tradeoff in exchange for lower tail risk.

1. The cash bucket approach. Keep one to three years of planned spending in Treasury bills, money market funds, or short-duration bond funds. When markets drop, fund withdrawals from the cash bucket rather than selling equities. The logic: a cash bucket is essentially insurance against the first year or two of a bad sequence.

The cost: the cash reserve earns less than the full portfolio would earn over a long horizon. Holding two years of spending in T-bills at 4.5% rather than in equities at an expected 7% is a drag. The insurance is not free. The tradeoff is accepting lower long-run return in exchange for lower sequence risk.

2. Dynamic withdrawal rules. Instead of withdrawing a fixed real amount each year, adjust withdrawals based on portfolio performance. Guyton-Klinger guardrails, developed by Jonathan Guyton in 2006, specify rules that cut withdrawals by 10% when the portfolio has fallen below a threshold and increase them when it has risen above another threshold. The Variable Percentage Withdrawal approach from the Bogleheads community takes a related but distinct approach, recalculating each year’s withdrawal as a percentage of the current portfolio balance.

The cost: variable income. A retiree using Guyton-Klinger or VPW needs to be able to cut spending in bad years. For retirees with high fixed expenses (mortgage, long-term care insurance, supporting other family members), dynamic rules are less practical.

3. Rising equity glidepath. Counter to traditional advice, research by Kitces and Pfau has argued that starting retirement at a lower equity allocation and raising it over time reduces sequence risk. The logic: if the worst sequences of returns hit in early retirement, holding more fixed income in the first decade protects against the worst outcomes. If those early years go well, the portfolio has enough cushion to hold more equity later without risking plan failure.

The cost: the strategy feels backwards. Most retirees’ intuition is that they should reduce equity exposure with age, not increase it. The academic argument is that the sequence-risk-adjusted math points the other way.

What this means for planning

A few things follow from sequence-of-returns risk that are worth carrying forward into any retirement plan.

The starting year matters, and it is outside the retiree’s control. No amount of good planning can guarantee a retirement that begins in a benign market. The only response is to build a plan that survives an ugly starting sequence, not one that depends on getting lucky.

A single fixed withdrawal rate is fragile. The 4% rule is defensible as a starting figure, but it is not a guarantee. Research suggests the defensible range is closer to 3.3% to 4.0% given current market conditions. A plan that commits to a rigid 4% in a bad sequence is likely to fail.

Flexibility is a form of insurance. Any strategy that allows the retiree to cut spending by 10-15% in bad years significantly reduces sequence risk. The cash bucket, dynamic rules, and the glidepath all do this in different ways.

Consider when you will start Social Security. A retiree who delays Social Security from 62 to 70 locks in a benefit that is roughly 77% higher in real terms. That higher floor reduces the withdrawal rate the portfolio must support, which in turn reduces sequence-of-returns exposure. For more on this decision, see our Social Security claiming guide.

Related reading

For more on retirement planning topics, see our retirement savings by age benchmarks, our 401(k) when you leave a job guide, and our note on asset allocation fundamentals.

This is educational content. Specific withdrawal rates, cash-bucket sizes, and glidepath allocations depend on the specific retiree. Please consult a qualified financial professional before making investment decisions.

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Ferrante Capital LLC is a registered investment adviser. Information presented is for educational purposes only and does not constitute investment advice, a solicitation, or a recommendation to buy or sell any security. All investing involves risk, including the possible loss of principal.

FC and its principals may hold positions in securities or asset classes discussed in this article. This analysis is for educational purposes only and does not constitute a recommendation to buy, sell, or hold any security.

Forward-looking statements reflect Ferrante Capital’s current analysis and involve assumptions and estimates. Actual results may differ materially. Past performance is not indicative of future results.

Please consult a qualified financial professional before making investment decisions.