The 4% Rule Isn't a Law of Physics: What Its Own Creator Says About Retirement Withdrawals Today

Even the Man Who Invented the 4% Rule Has Rethought It

If you've read anything about retirement income, you've run into the 4% rule: withdraw 4% of your portfolio in your first year of retirement, adjust that dollar amount for inflation each year after, and — according to the original research — your money should last at least 30 years. It's simple, it's memorable, and it's been treated almost like a law of physics for three decades. There's just one problem: the person who created it has spent recent years explaining why it shouldn't be treated that way.

Where the 4% Number Actually Came From

Financial planner Bill Bengen published the original research behind the rule in 1994. Using historical market data going back to 1926, he tested withdrawal rates against every rolling 30-year retirement period in that data and found that 4.15% was the worst-case withdrawal rate — the lowest a retiree could have gotten away with, in the single worst historical period, and still not run out of money over 30 years.

That detail matters, because it means the number was never meant to be a target. It was a floor, calculated from the worst stretch in the data. Bengen himself has pointed out that 99.5% of the retirement periods in his own research could have supported a higher withdrawal rate than 4% — in many cases, a much higher one.

What Bengen Says Now

In recent interviews, Bengen has described the 4% figure as having real but limited value, calling it a guide "for the ultra-conservative individual." He's since introduced the idea of a "safe max" — the highest withdrawal rate that's actually safe for a specific person's situation, rather than one fixed number applied to everyone. In one widely cited interview, he noted that expanding his original model to include a broader mix of asset classes pushed the sustainable rate up toward 4.7%, and that he suspects the real number, with still more diversification, could be closer to 5%.

The point isn't that 4.7% or 5% is the new magic number either. It's that your safe max depends on your own time horizon, how your money is invested, which accounts you're drawing from, and whether you want to leave money behind for family. A single flat percentage was never going to capture all of that.

Why This Myth Causes Real Problems

Treating 4% as a hard rule tends to push people toward one of two mistakes:

• Underspending out of fear. Retirees who rigidly stick to 4% — or go even lower out of caution — can end up living more frugally than they ever needed to, leaving money unused that could have funded travel, family time, or simply a more comfortable retirement.
• Overexposure to market risk. Because the rule assumes a portfolio invested for growth over a multi-decade horizon, leaning on it alone can leave essential expenses tied to markets that don't always cooperate, especially early in retirement when a downturn does the most damage.

A Steadier Way to Think About It

Instead of asking "What percentage can I withdraw?", a more useful question is: "What are my bills, and what's actually guaranteed to cover them?" Separating your retirement income into what covers essentials versus what funds extras changes the whole conversation. Guaranteed sources — Social Security, pensions, and income from a fixed annuity with an income rider — can be matched directly against essential expenses, so that question of "safe withdrawal rate" only has to apply to the portion of your money that's genuinely discretionary.

Takeaway

The 4% rule isn't wrong, exactly — it's just far narrower than the way most people use it. It was built as a worst-case floor for one way of structuring a portfolio, not a universal formula for every retiree. If your plan currently leans entirely on a withdrawal percentage to cover your real, non-negotiable bills, it's worth stepping back and asking what portion of your income is actually guaranteed versus what's riding on the market doing its part.

Sources: Bill Bengen's original 1994 research, as widely cited in financial planning literature; "Bill Bengen Explains Why the 4% Rule Is Now 4.7%," paytaxeslater.com interview transcript, 2026. This article is educational only and not personalized financial advice. It does not predict or guarantee market performance, and guarantees on any annuity are subject to the terms of the specific contract and the issuing insurance company's claims-paying ability.