Is the 4% Rule Leaving Money on the Table?

For thirty years, retirement planning has orbited one number: 4%. Withdraw four percent of your portfolio in year one, raise it with inflation every year after, and — per the famous research — a balanced portfolio historically survived 30 years. It's simple, it's disciplined, and according to Morningstar's latest research, it may be quietly costing careful retirees the retirement they actually saved for.

What the new research found

Morningstar's baseline "safe" withdrawal rate for someone retiring in 2026 is 3.9% — even more conservative than the classic rule. But that number assumes you rigidly spend the same inflation-adjusted amount every year no matter what markets do. When portfolio strategist Amy Arnott's team tested eight flexible spending strategies — approaches that adjust withdrawals as conditions change — the picture transformed. The best-performing methods supported starting withdrawal rates as high as 5.7%.

The standout was a probability-based guardrails approach — raising or trimming spending based on the plan's ongoing odds of success. Over a 30-year retirement, Morningstar found it generated roughly $1.55 million of lifetime spending versus $1.18 million for the fixed 3.9% approach: about $370,000 more, a 31% increase, with relatively modest year-to-year volatility. Arnott's observation: it's the method that most resembles what a good advisor already does — revisit the plan regularly and adjust, rather than obey a formula set on day one.

Why rigid rules overshoot

The 4% rule's deepest assumption is that retirees spend the same real amount at 90 as at 65. Real households don't. The research Morningstar cites shows inflation-adjusted spending falls about 19% between 65 and 75, 34% by 85, and 52% by 95 — the "go-go" years give way to slower ones, and a rule that ignores that arc forces the deepest frugality exactly when you'd enjoy spending most.

The catch — and it matters

• Flexible means down, not just up. Every higher-spending strategy works because it cuts spending after bad markets. If your budget can't flex, neither can your withdrawal rate.
• Allocation still does the heavy lifting. The research found balanced portfolios — roughly 30–50% equities — produced the strongest retirement-income results.
• The inputs are personal. Social Security timing, pensions, annuity income, long-term-care exposure, and sequence-of-returns risk all move your number. A headline rate — 4%, 3.9%, or 5.7% — is a starting point for analysis, not an answer.