Photo by Katie Harp on Unsplash
Data freshness note: all statistics and rates cited below reflect publicly available sources current as of June 30, 2026.
- As of June 30, 2026, two authoritative research sources disagree on safe retirement withdrawals by 1.6 percentage points — Morningstar says 3.9%, while the rule's own creator now endorses 5.25%–5.5%.
- Morningstar's December 2025 State of Retirement Income report sets the 2026 safe rate at 3.9% for portfolios with 30–50% equity allocation, up from 3.7% in 2025.
- William Bengen, who created the 4% rule in 1994, now recommends 5.25%–5.5% in his August 2025 book, citing broader diversification into mid-cap, small-cap, micro-cap, and international equities.
- Retirees using a flexible "guardrails" approach — adjusting spending based on market performance rather than a fixed rate — may sustainably withdraw as much as 5.7% annually.
The Common Belief
1.6 percentage points. On a $1 million investment portfolio, that gap — between Morningstar's 2026 recommendation of 3.9% and William Bengen's updated guidance of 5.5% — translates to $16,000 in annual spendable income. Stretched across a 30-year retirement with compounding and portfolio longevity effects, that divergence between two of the most credible sources in retirement research represents a fundamentally different financial life.
Since Bengen published his landmark analysis in 1994, the 4% rule has been financial planning's most durable shorthand. The original framework assumes a 50/50 portfolio split between equities (stocks) and fixed income (bonds), with the retiree withdrawing 4% of their opening balance in year one and adjusting that dollar amount each subsequent year for inflation. It survived the dot-com bust, the 2008 financial crisis, and a prolonged era of near-zero interest rates. Retirement projections, robo-advisor algorithms, and advisor spreadsheets built their scaffolding around it.
Investopedia recently examined this debate extensively — as reported through Google News — and the picture that emerges is considerably more fractured than conventional wisdom suggests. The 4% rule isn't dead. But treating it as a universal constant may be leaving money on the table for some retirees while dangerously overexposing others.
Where the Certainty Cracks
Two of the most credible voices in retirement research are pointing in opposite directions. Morningstar's December 2025 State of Retirement Income report concluded that the safest starting withdrawal rate for a typical person retiring in 2026 is 3.9% — assuming a 90% probability of funds surviving a 30-year horizon with a portfolio holding 30–50% equities. That figure actually improved from 3.7% in 2025, reflecting higher expected returns across asset classes partially offset by projected inflation rising from 2.29% to 2.46%, per Morningstar's forward-looking capital market models.
Bengen's trajectory runs the opposite direction. In his August 2025 book A Richer Retirement, he argues that his original worst-case SAFEMAX (the safest withdrawal rate even under the most punishing historical market sequences) should be revised upward from 4.15% to 4.7%. His broader estimate for current retirees: 5.25%–5.5%. The driver is diversification. Bengen's updated research incorporates mid-cap, small-cap, micro-cap, and international equity positions — asset classes absent from the original 1994 analysis — producing meaningfully better portfolio resilience under stress scenarios.
MoneyWise highlighted this stark divergence specifically: the person who invented the 4% rule is now recommending a rate roughly 1.6 percentage points above what Morningstar's institutional research endorses. Both conclusions are backed by rigorous back-testing. The difference is methodological — Morningstar uses forward-looking assumptions anchored to current market valuations; Bengen relies on historical worst-case return sequences. They are technically answering different versions of the same question.
Chart: Safe annual withdrawal rate estimates from major 2025–2026 research. Sources: Morningstar (December 2025 State of Retirement Income), Bengen (August 2025), current guardrails research.
The guardrails figure at the far right of that chart is arguably the most actionable data point. Retirees who spend more when markets perform well and pull back when they don't can sustain withdrawals as high as 5.7% annually — 46% above Morningstar's conservative fixed-rate figure — without meaningfully increasing the probability of running out of money. The guardrails model reframes the withdrawal question: instead of finding the maximum safe starting rate and holding it forever, the goal becomes building a spending system that adapts to what markets actually deliver.
Prudential's financial education resources and Charles Schwab's retirement planning tools both point to a risk that neither headline percentage captures: sequence-of-returns risk. This is the danger that a market downturn early in retirement permanently depletes a portfolio — even if long-run returns eventually recover — because withdrawals at a fixed rate accelerate portfolio depletion when asset values are already falling. The starting conditions of a retirement matter as much as long-run averages, which is why a single universal rate struggles to hold across different entry points.
Photo by Md Ishak Rahman on Unsplash
AI Is Reshaping Retirement Income Modeling
The fixed-versus-dynamic withdrawal debate has a new participant: artificial intelligence. As of June 30, 2026, robo-advisors manage over $1.8 trillion in U.S. assets — up from $1.4 trillion at the start of 2025. Vanguard's AI-powered retirement tools, updated in 2026, now automatically adjust withdrawal recommendations based on real-time market conditions and actual spending patterns, a meaningful shift from the static rule-based era those platforms were built on.
These AI investing tools can simulate thousands of retirement scenarios simultaneously, optimize tax efficiency across Social Security, pension, and investment income streams, and flag portfolio drift toward a danger zone before a retiree notices. For personal finance planning at scale, that's a genuine advancement. But industry analysts consistently note that current AI platforms struggle with the genuinely complex decumulation-phase decisions — long-term care cost modeling, estate planning trade-offs, the behavioral challenge of spending down accumulated savings — that don't reduce cleanly to algorithmic inputs.
My read: AI-driven robo-advisors are best understood as a low-cost automated implementation of the guardrails concept, not a replacement for the underlying strategic framework. They handle the execution. The question of which framework to build on — fixed rate, guardrails, dynamic sequencing — still requires human judgment, because the inputs (spending flexibility, health trajectory, risk tolerance) are deeply personal.
A Better Frame for Your Financial Planning
The 4% rule's enduring value was never the number — it was the discipline of having a number at all. A systematic withdrawal strategy, applied consistently and inflation-adjusted, outperforms ad hoc spending decisions in nearly every historical scenario. The Morningstar versus Bengen disagreement is really a methodological debate about assumptions, not a verdict on whether systematic withdrawals work. The more important evolution is away from any rigid universal rate and toward strategies that adapt.
Run your retirement projections under a scenario where the first five years produce negative real returns. Monte Carlo simulation tools — available free through most major brokerage platforms — reveal whether your withdrawal rate survives a bad-start scenario, not just a historically average one. A retirement plan that only holds if markets cooperate immediately is a bet dressed up as a plan.
Instead of locking into a fixed annual withdrawal adjusted only for inflation, set defined guardrails upfront: reduce spending by roughly 10% if your portfolio drops below a threshold you set in advance, allow a modest increase if it rises meaningfully above plan. Research supports these adaptive strategies at rates up to 5.7% — significantly above Morningstar's 3.9% fixed-rate figure — because the built-in flexibility reduces the probability of catastrophic depletion over long time horizons.
Bengen's revised SAFEMAX of 4.7% and his broader 5.25%–5.5% guidance both depend on investment portfolios that include mid-cap, small-cap, micro-cap, and international equities — not solely large-cap U.S. stocks and intermediate Treasuries. If your retirement portfolio is concentrated in S&P 500 index funds and bond funds, you may be accepting unnecessarily lower withdrawal capacity through under-diversification. With U.S. life expectancy at 78.4 years as of 2023, and over 100,000 centenarians living in the United States as of 2024, the longevity math increasingly demands portfolios built to sustain 35 to 40 years, not just the 30-year horizon most rules assume.
Frequently Asked Questions
What is the 4% rule for retirement, and how does it actually work?
The 4% rule was developed by financial planner William Bengen in 1994. It holds that retirees can withdraw 4% of their starting portfolio balance in year one, then adjust that dollar amount annually for inflation, with the expectation that funds will last at least 30 years. The original analysis assumed a 50/50 portfolio split between stocks and bonds. It functions as a planning heuristic — a useful starting framework — not a mathematical guarantee of any specific outcome.
Is the 4% rule outdated for retirement planning in today's environment?
It's actively contested rather than simply outdated. As of June 30, 2026, Morningstar's research recommends 3.9% for 30-year horizons, while Bengen himself now endorses 5.25%–5.5% based on expanded portfolio diversification. Neither position is wrong — they reflect different analytical methodologies applied to the same underlying question. The more meaningful shift is from any single fixed rate toward flexible, market-responsive strategies that current research supports at rates up to 5.7%.
Can I retire with a 4% withdrawal rate if I plan for a 40-year retirement?
A longer retirement horizon materially changes the math. Bengen's original 4% figure targeted a 30-year window. U.S. life expectancy reached 78.4 years in 2023, and over 100,000 centenarians live in the United States as of 2024 — meaning a growing cohort of retirees faces 40-year-plus spans. Longer horizons require more conservative starting rates or robust guardrails strategies. Morningstar's 3.9% already assumes a 30-year window; early retirees or those with family longevity history typically need to plan more conservatively than that baseline.
What happens if I consistently withdraw more than 4% from my retirement portfolio?
Sustained over-withdrawal doesn't trigger immediate problems — in strong markets, it can work for years without visible strain. The real danger is sequence-of-returns risk: if a significant market decline occurs in the early years of retirement while withdrawals are running high, the portfolio may never fully recover even if markets subsequently perform well. This is why Prudential and Charles Schwab's retirement planning resources both emphasize that starting conditions — not just long-run averages — are the central variable in retirement income planning.
Disclaimer: This article is for informational and educational purposes only and does not constitute financial or investment advice. Always consult a qualified financial professional before making retirement planning decisions. Research based on publicly available sources current as of June 30, 2026.