The "4% Rule" isn't a law of nature, but it exists because of a mathematical "monster" called
Sequence of Returns Risk (SORR).
To put it simply: In retirement, the
order in which you get your investment returns matters just as much as the
average return.
The Core Concept
If you were just saving money (the "accumulation phase"), a bad year in the market is actually a "sale" on stocks. But when you are withdrawing (the "decumulation phase"), a bad year at the start can be a permanent wound to your portfolio.
Why the "Average" is a Trap
Imagine two retirees, both starting with $1M and both averaging a
7% annual return over 3 years.
| Year | Retiree A (Good Sequence) | Retiree B (Bad Sequence) |
| Year 1 | +20% | -20% |
| Year 2 | +7% | +7% |
| Year 3 | -20% | +20% |
| Average | 7% | 7% |
If they weren't touching the money, they’d end up with the same amount. But if they are both
withdrawing $50,000 a year, Retiree B is in big trouble. Retiree B is forced to sell shares when the price is low to make that $50k withdrawal, "locking in" those losses and leaving less capital behind to grow when the market finally recovers.
Why 4%?
The 4% Rule (derived from the Trinity Study) was designed to survive the "Worst Case Scenarios" in history—like retiring right before the Great Depression or the stagflation of the 1970s.
- The Math of Recovery: If your portfolio drops 50% in Year 1, you need a 100% gain just to get back to even. If you are also pulling money out during that 50% drop, the "climb back up" becomes mathematically impossible.
- Inflation Protection: That 4% usually needs to increase every year to keep up with the cost of living. If the market is down and your withdrawal amount is going up, the "burn rate" accelerates.
How to Fight Sequence Risk
Your friend doesn't necessarily have to stick to a rigid 4% forever, but they should have a plan for those first 5–10 years of retirement:
- The "Bucket" Strategy: Keep 2–3 years of cash in a high-yield savings account so you don't have to sell stocks during a market crash.
- Dynamic Spending: Agree to skip the "inflation raise" or cut spending by 10% in years when the market is down.
- Guardrails: Only increase spending when the portfolio hits certain high-water marks.
Bottom Line: Sequence risk is like a plane takeoff. If you hit turbulence right as you're leaving the ground, it's much more dangerous than hitting it once you're at cruising altitude.
Would you like me to run a quick simulation or a table showing how a "Bad Sequence" specifically drains a portfolio over 10 years?
To show why this is so dangerous, let’s look at two people—
Steady Stan and
Unlucky Ursula.
Both start with
$1,000,000, both withdraw
$50,000 a year (5% initial rate), and both see an
average return of 5% over five years. The only difference is the
order of those returns.
The "Sequence of Returns" Showdown
| Year | Market Return | Stan's Balance (Good Start) | Ursula's Balance (Bad Start) |
| Start | — | $1,000,000 | $1,000,000 |
| Year 1 | Stan +15% / Ursula -15% | $1,100,000 | $800,000 |
| Year 2 | +10% | $1,160,000 | $830,000 |
| Year 3 | +5% | $1,168,000 | $821,500 |
| Year 4 | -10% | $1,001,200 | $689,350 |
| Year 5 | Stan -15% / Ursula +15% | $801,020 | $742,752 |
Note: Calculations assume the withdrawal is taken at the end of the year for simplicity.
The Damage Assessment
Even though the market performed identically over the 5-year period for both people:
- Stan is in great shape. Even after a rough Year 4 and 5, he still has over 80% of his original nest egg.
- Ursula is in a "death spiral." Because she had to pull out $50,000 when her portfolio was already crashing in Year 1, she had less money left to catch the recovery in Year 5. She is nearly $60,000 poorer than Stan, despite the same average market performance.
The "Feedback Loop" Problem
This is why the 4% rule is so conservative. If Ursula had been withdrawing
7% ($70k), her portfolio would have been cannibalized so quickly in those first two years that she might never have recovered, regardless of how well the market did later.
In math terms, the formula for your remaining balance $B$ after a year with return $r$ and withdrawal $W$ looks like this:
$$B_{new} = B_{old}(1 + r) - W$$
When $r$ is negative in the early years, the subtraction of $W$ (the withdrawal) happens against a shrinking base, compounding the loss.
www.eonline.com
