For three decades, the 4% rule has been the bedrock of retirement planning. Financial advisors built empires on it. The FIRE community memorized it as gospel. Millions of Americans calculated their “magic number” by multiplying annual expenses by 25.
Now, the man who invented it says we’ve been doing it wrong.
In December 2025, Bill Bengen released A Richer Retirement: Supercharging the 4% Rule, formally updating his landmark 1994 research. His new recommendation? A 4.7% safe withdrawal rate—a 17.5% increase that could fundamentally change how you plan for financial independence.
What Changed: The Data Bengen Didn’t Have in 1994
When Bengen published his original study, he was working with limited historical data and conservative assumptions designed for worst-case scenarios. His 4% SAFEMAX rate was calculated specifically to survive conditions like those retirees faced in 1968—right before the brutal bear market and stagflation of the 1970s.
Here’s what Bengen himself admitted in subsequent research: the 4% rule was essentially planning for the Great Depression to start the moment you retire. For most retirees throughout history, that level of conservatism meant leaving significant money on the table.
By incorporating decades of additional market data and refining his analytical methodology, Bengen now concludes that retirees who stick rigidly to 4% are “cheating themselves.”
What 4.7% Actually Means for Your Retirement Number
The math is straightforward but the implications are profound:
Under the 4% Rule:
- Required portfolio for $50,000 annual spending: $1,250,000
- Required portfolio for $80,000 annual spending: $2,000,000
Under the 4.7% Rule:
- Required portfolio for $50,000 annual spending: $1,063,830
- Required portfolio for $80,000 annual spending: $1,702,128
That’s nearly $200,000 less you need to save for a $50,000 lifestyle—or roughly 3-5 additional years of work eliminated from your timeline.
For the FIRE community, this isn’t just academic. It’s the difference between retiring at 45 versus 50, or between lean FIRE and comfortable financial independence.
But Wait: The Important Caveats
Before you raid your portfolio, Bengen’s updated guidance comes with critical nuances that most headlines ignore:
The 4.7% rate assumes:
- A 30-year retirement horizon
- A balanced portfolio (typically 50-75% equities)
- The ability to remain invested during downturns
- No catastrophic early sequence of returns
During periods of elevated inflation or when market valuations are extreme, Bengen acknowledges the safe rate may differ. His research shows withdrawal rates can climb even higher during periods of low to moderate inflation—but can also drop during sustained high-inflation environments.
What Morningstar’s Annual Analysis Reveals
Meanwhile, Morningstar’s 2025 retirement income research offers a more conservative counterpoint. Their forward-looking analysis, which incorporates current bond yields and equity valuations, suggests a 3.9% starting withdrawal rate for those retiring in 2026.
Why the discrepancy? Bengen’s methodology relies on historical backtesting—what worked in the past. Morningstar’s approach uses capital market expectations for future returns, which currently project lower yields than historical averages.
This isn’t a contradiction. It’s a reminder that “safe” withdrawal rates depend heavily on your assumptions.
The Real Solution: Move Beyond Static Rules Entirely
Here’s what the debate between 3.9% and 4.7% actually reveals: static withdrawal rules—no matter how carefully calculated—are inherently limited.
As research from Charles Schwab demonstrates, your optimal withdrawal rate depends on variables that can’t be captured in a single percentage:
- Your specific asset allocation (bond-heavy portfolios require lower rates)
- Your planned retirement duration (40+ years for early retirees vs. 25 for traditional retirees)
- Your flexibility (can you reduce spending during market downturns?)
- Your other income sources (Social Security, pensions, rental income)
- Sequence of returns (when good and bad market years occur)
The solution isn’t finding the “right” percentage. It’s understanding the probability distribution of outcomes for your specific situation.
How Monte Carlo Analysis Resolves the Withdrawal Rate Debate
While pundits argue over 3.9% vs. 4% vs. 4.7%, sophisticated retirement planning has moved beyond static rules entirely.
Monte Carlo simulation—the same technique used by institutional investors and wealth managers—doesn’t give you a single “safe” number. Instead, it runs your retirement plan through thousands of possible market scenarios and tells you the probability of success.
Consider the difference:
Static Rule Approach: “Withdraw 4.7% and hope for the best.”
Monte Carlo Approach: “Given your specific portfolio, spending, and timeline, your plan succeeds in 847 out of 1,000 scenarios at 4.7% withdrawal—but drops to 720 scenarios if you retire during a bear market.”
That probability-based framing transforms retirement planning from guesswork into informed decision-making.
What This Means for Early Retirees
The FIRE community should pay particular attention to Bengen’s update—and its limitations.
Early retirees face extended time horizons (40-50 years vs. the 30-year standard), making them more vulnerable to:
- Sequence of returns risk: Poor early returns can devastate a portfolio that needs to last decades
- Inflation compounding: Even modest inflation becomes significant over 40+ years
- Healthcare costs: The pre-Medicare gap adds substantial uncertainty
Bengen’s 4.7% rate, while more generous than his original guidance, still assumes a 30-year horizon. For a 40-year early retirement, research from the Trinity Study suggests more conservative initial withdrawals may be prudent—unless you have flexibility to adjust spending during downturns.
The Bottom Line: Test Your Plan, Don’t Trust Rules
Bill Bengen’s 4.7% update is significant—it suggests millions of retirees have been unnecessarily conservative. But the real lesson isn’t that 4.7% is the new magic number.
The lesson is that your retirement confidence shouldn’t rest on any static rule.
Whether markets favor Bengen’s optimism or Morningstar’s caution, the retirees who succeed will be those who:
- Understand the probability distribution of their outcomes
- Build in flexibility to adjust during adverse conditions
- Test their plans against realistic market scenarios—not just historical averages
The 4% rule was never meant to be a guarantee. Neither is 4.7%. But probability-based planning can give you something better than false certainty: genuine confidence grounded in data.
Ready to see how your retirement plan performs across thousands of market scenarios? The Retirement Success Graph app brings professional-grade Monte Carlo analysis to your iPhone—the same probability-based modeling that financial advisors use for their wealthiest clients. Test your plan in seconds, not spreadsheet hours.
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