Guides · Tax strategy & estate
FIRE Withdrawal Strategies & the 4% Rule
The 4% rule came out of research into 30-year retirements. FIRE borrows it for retirements that might last fifty — which is the assumption worth examining before you build a life on it.
What the research actually tested
Bengen's 1994 work asked a specific question: what starting withdrawal rate, increased with inflation each year, would have survived every historical 30-year period? The answer was about 4%. The Trinity study a few years later examined success rates across various rates and allocations, reaching broadly similar conclusions by a different route.
Read the conditions, because they're doing as much work as the number. A 30-year horizon. A US stock and bond portfolio, with equity allocations tested roughly between 50% and 75%. Withdrawals rising mechanically with inflation regardless of what markets did. And historical US returns, which were unusually good by global standards.
Change any of those and 4% stops being the answer to your question. Someone retiring at 40 is planning for fifty years, not thirty, and the longer the horizon the lower the rate that survives it.
25× annual spending is just 1 ÷ 0.04. Change the rate and the multiplier changes with it.
The order of returns, not just the average
Two retirees can experience identical average returns over thirty years and end up in completely different places. What separates them is when the bad years arrived.
Withdrawing a fixed amount from a falling portfolio means selling more shares to raise the same cash, permanently shrinking the base that has to recover. A poor first five years does damage that a strong final five cannot undo, because there's less left to grow. That's sequence-of-returns risk, and it is what actually breaks retirements at a 4% rate — not low average returns.
The defences are unglamorous. Hold a bond and cash sleeve you can spend from so you're not forced to sell equities into a decline. Stay willing to cut spending in a bad year — flexibility is worth more than any allocation tweak. And treat the first few years after you stop working as the period with the least margin for error, rather than the most.
The number you spend isn't the number you withdraw
Withdrawal-rate research measures gross portfolio withdrawals. Your spending happens after tax, and the gap between the two is easy to plan straight past.
Money coming out of a traditional 401(k) or IRA is ordinary income, so $60,000 of spending needs meaningfully more than $60,000 of withdrawals. Roth withdrawals are untaxed, and a taxable brokerage account sits in between — only the gain portion is taxed, at capital-gains rates.
Which is why the account mix matters as much as the total. A retiree drawing from all three can control their taxable income year by year, which in turn controls their bracket and, before Medicare age, their health insurance subsidies. The same portfolio can fund noticeably different lifestyles depending on where the money sits.
4% was a finding about a 30-year horizon and a specific portfolio mix, not a law. It's a good planning anchor, and a longer retirement, taxes, and a bad first few years all push the sustainable number lower.