The 4% Rule: Does It Still Work? How It Fails and What to Use Instead

You saved for 30 years. You hit your number. You retire on a Friday, and by Monday morning you face the single most consequential financial question of your life: how much can I actually spend?

The 4% rule is supposed to answer that question. It says you can withdraw 4% of your portfolio in Year 1, adjust for inflation every year after, and your money will last 30 years. Simple. Clean. Reassuring. And depending on who you ask in 2026, either too conservative by almost a full percentage point or dangerously aggressive.

The short version: The 4% rule is a useful starting point, not a law. Morningstar's 2025 research suggests 3.9% is safer for fixed withdrawals. William Bengen (the rule's creator) now says 4.7% works with a diversified portfolio. The real answer: be flexible with your spending, and you can start closer to 5%.

Where the 4% Rule Came From

In 1994, a financial planner named William Bengen published a paper in the Journal of Financial Planning that changed retirement planning forever [1]. He tested every 30-year retirement period going back to 1926, using a portfolio split 50/50 between the S&P 500 and intermediate-term government bonds. His question was straightforward: what's the highest withdrawal rate that survived the worst period in history?

The answer was about 4%. The worst starting year turned out to be 1966 (high inflation, flat stock market, ugly bonds). Even then, 4% survived.

Four years later, three professors at Trinity University expanded the analysis in what became known as the Trinity Study [2]. They confirmed Bengen's findings and popularized the idea. The "4% rule" entered the vocabulary of every retirement planner, financial advisor, and early-retirement blogger on the internet.

Here's what people forget: Bengen's paper was never a rule. It was a floor. The worst-case starting point for one specific portfolio. Most historical periods supported withdrawal rates of 5%, 6%, even higher. The 4% was only necessary if you retired into the worst economic conditions in modern American history and never adjusted your spending.

What the Rule Gets Right

Give it credit. The 4% rule solved a real problem.

Before Bengen's work, retirees either guessed, or they relied on simplistic formulas like "spend only the interest." The 4% rule gave people a concrete, testable number backed by nearly 70 years of market data. It introduced the concept of inflation-adjusted withdrawals (you don't just take $40,000 forever; you increase that amount each year with inflation). And it highlighted something most retirees hadn't thought about: sequence of returns risk, the danger that a bad market in your first few years could doom a portfolio that looks fine on paper.

For someone retiring at 65 with a 30-year horizon, the rule remains a reasonable starting place. Not a bad one.

But "reasonable starting place" and "optimal strategy" are different things.

Three Ways the 4% Rule Fails

It Ignores Taxes and Fees

The 4% is a gross number. If you pull $50,000 from a Traditional IRA, you owe income tax on every dollar. Depending on your bracket, your actual spending money might be $42,000 or $38,000. Investment fees eat another slice. The original research didn't account for either [3].

It Assumes You Never Adjust

The rule says you take $50,000 in Year 1, then $51,500 in Year 2 (adjusting for inflation), then $53,045 in Year 3, regardless of what the market does. Your portfolio drops 30%? You still ratchet up your withdrawals. That's the math. And it's absurd. No actual human being would do this.

Real retirees skip the vacation when markets crash. They spend more when their portfolio is up 25%. The rule's rigid framework ignores the single most powerful tool retirees have: flexibility.

It May Not Fit Your Timeline

Bengen designed the rule for a 30-year retirement. Retire at 65, and 30 years gets you to 95. That works for many people. But the average American retires at 62 [4], and if you're part of the FIRE movement retiring at 45, you need your money to last 40 to 50 years. For longer horizons, research suggests the safe rate drops to 3.25% or even lower [5].

And it works the other way too. A 75-year-old who only needs 15 years of withdrawals? 4% is probably too conservative. They're leaving money on the table.

What the Latest Research Says

The debate over the "right" number has produced some surprising disagreements.

Morningstar's 2025 annual retirement income study pegged the safe starting rate at 3.9% for someone using a fixed, inflation-adjusted strategy [6]. That's actually up from 3.7% in their 2024 report, thanks to somewhat better bond yields. The 10-year Treasury was yielding about 4.14% as of early 2026 [7], which helps.

But here's the twist. The same Morningstar report found that retirees willing to use dynamic spending methods (cutting back in down years, spending more in up years) could start at 5.7% [6]. That's not a typo. Nearly six percent. The gap between the rigid and flexible approaches is almost two full percentage points.

Meanwhile, Bengen himself published new research in 2025 arguing the safe floor should be 4.7%, not 4.0% [8]. The difference? His updated analysis uses a more diversified portfolio that includes small-cap stocks, mid-cap stocks, and international equities, not just the S&P 500 and government bonds. Broader diversification raised the worst-case survival rate.

So who's right? Honestly, all of them. They're answering slightly different questions with slightly different assumptions. The common thread: rigid rules underperform flexible strategies by a wide margin.

(I'll admit something: I find it oddly reassuring that the guy who invented the rule now says it's too conservative. If even Bengen thinks you can spend more, maybe the rest of us can relax a little.)

A Worked Example: Three Approaches, One Couple

Meet David and Linda, both 65, retiring with $1,250,000.

Approach 1: Strict 4% Rule Year 1 withdrawal: $1,250,000 × 4% = $50,000. Year 2 (assuming 3% inflation): $51,500. They take this amount regardless of what the market does.

Approach 2: Morningstar's 3.9% Base Year 1: $1,250,000 × 3.9% = $48,750. Year 2: $50,213. A slightly smaller paycheck, but a higher probability of not running out of money over 30 years.

Approach 3: Guardrails (Starting at 5%) Year 1: $1,250,000 × 5% = $62,500. But here's the deal: if the market crashes and their current withdrawal rate exceeds 6% of the remaining portfolio, they cut spending by 10%. If the portfolio booms and their rate drops below 4%, they give themselves a 10% raise.

Scenario: the market drops 20% in Year 2. David and Linda's portfolio falls to roughly $937,500 after their withdrawal. Their planned Year 2 spending (with inflation) would be about $64,375. That's 6.9% of the remaining portfolio, which triggers the guardrail. They cut to $57,938. It's a smaller paycheck than planned, but still $7,000 more per year than the rigid 4% approach. And their portfolio survives.

The guardrails approach (developed by Jonathan Guyton and William Klinger in 2006) isn't free money [9]. The trade-off is income volatility. Some years you spend less than you'd like. But the starting point is meaningfully higher, and the probability of portfolio survival remains above 95%.

What About FIRE Retirees?

If you're retiring at 40 or 45 and need your portfolio to last 50 years, the math changes. A lot.

Vanguard's 2026 outlook projects annualized U.S. equity returns of 3.4% to 5.4% over the next decade [10], well below the historical average of roughly 10%. Lower expected returns mean a longer retirement requires a lower starting rate.

For a 50-year horizon, most researchers suggest 3.25% to 3.5% as a fixed starting point. But again, flexibility changes everything. If you're willing to get a side gig during a bear market or cut discretionary spending by 20% when your portfolio drops, 4% might be fine even over five decades.

This is where it's worth being honest with yourself. "I'll just cut spending" sounds easy in a spreadsheet. It's harder when your dishwasher breaks, your kid needs help, and the market is down 35%.

Your Next Move

1. Run your own numbers. Use our compound interest calculator to model different withdrawal rates against your actual portfolio size and timeline. Small rate changes compound into six-figure differences over 30 years.

2. Pick a flexible strategy, not a fixed rate. The guardrails approach or Morningstar's dynamic spending model outperform rigid rules in nearly every historical scenario. If your spending can flex by 10–15% in bad years, you can safely start higher.

3. Diversify beyond the S&P 500. Bengen's updated research shows that adding small-cap value, mid-cap, and international stocks raises the worst-case survival rate. Consider Vanguard's VTI (total U.S. market) plus VXUS (total international) rather than just an S&P 500 fund.

4. Build a tax-efficient withdrawal strategy. The 4% rule doesn't account for taxes. Pulling money from the right accounts in the right order can save you thousands per year.

5. Revisit annually. The "right" withdrawal rate changes as your portfolio grows or shrinks, as bond yields shift, and as your spending needs evolve. A set-it-and-forget-it approach is exactly what the original rule promised, and exactly what the latest research says you shouldn't do.

References

1. Bengen, W. P. (1994). Determining Withdrawal Rates Using Historical Data. Journal of Financial Planning.
2. Cooley, P. L., Hubbard, C. M., & Walz, D. T. (1998). Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable. AAII Journal (The "Trinity Study").
3. Charles Schwab. (2025). Beyond the 4% Rule: How Much Can You Spend in Retirement? Schwab.com. https://www.schwab.com/learn/story/beyond-4-rule-how-much-can-you-spend-retirement
4. MassMutual/Gallup. (2024). Average Retirement Age Data. NerdWallet. https://www.nerdwallet.com/retirement/learn/average-retirement-age-us
5. Kiplinger. (2025). Is the 4% Rule Still a Good Guideline for FIRE Retirees? Kiplinger.com.
6. Arnott, A. C., Benz, C., Kephart, J., & Guo, T. (2025). The State of Retirement Income: 2025. Morningstar.
7. U.S. Department of the Treasury. (2026). Daily Treasury Par Yield Curve Rates. Treasury.gov.
8. Bengen, W. P. (2025). A Richer Retirement: Supercharging the 4% Rule to Spend More and Enjoy More. Wiley.
9. Guyton, J. T., & Klinger, W. J. (2006). Decision Rules and Maximum Initial Withdrawal Rates. Journal of Financial Planning.
10. Vanguard. (2026). Vanguard Economic and Market Outlook 2026.