For decades, retirement spending in America has been defined by the 4% rule. Withdraw that much from your portfolio in year one, adjust for inflation every year after, and your money should last three decades. The 4% rule gave an entire generation of savers a starting point they never had before.
But despite being clean and memorable, the 4% rule is also too simplistic for today’s retirement landscape.
Where the Number Came From
Financial planner William Bengen introduced the concept in a 1994 paper for the Journal of Financial Planning. He tested withdrawal rates against historical market returns going back to 1926 and found that a 4.15% starting withdrawal, adjusted annually for inflation, had never failed to fund a 30-year retirement. The industry rounded it down, and the 4% rule was born.
Bengen built the model on a simple 50/50 mix of large-cap stocks and intermediate-term government bonds. He designed it to survive the worst-case scenarios in the data, including the Great Depression and the high-inflation years of the 1970s. For a single-number rule of thumb, it held up remarkably well for a long time.
Why 4% No Longer Applies
Retirement itself has changed since 1994. People are living longer, which means a 30-year time horizon undersells what many retirees today need. Portfolios have also changed significantly since the original study; investors now hold small-cap, mid-cap, and international equities alongside domestic large-caps, a mix Bengen's original research never tested.
Bengen has revised his own number more than once. He moved to 4.5% in 2006, and in his more recent research, based on a broader portfolio that includes small and mid-cap stocks along with international exposure, he has pointed to a worst-case starting rate closer to 4.7%. Other researchers have suggested different rates. Morningstar's own State of Retirement Income research has put its base-case safe withdrawal rate at 3.7% in recent years, rising to 3.9% for 2026, reflecting more conservative forward-looking return assumptions for stocks and bonds alike.
A Static Number for a Dynamic Problem
A single fixed percentage should always have been seen as an estimated starting point, not a hard and fast rule.
The 4% rule assumes a retiree withdraws the same inflation-adjusted amount every single year, regardless of what markets are doing. Real retirees don't spend that way, and research increasingly suggests they don't need to.
Guardrail strategies, most notably the Guyton-Klinger approach, replace the fixed percentage with upper and lower spending limits. When the portfolio grows faster than expected, the retiree can spend more. When performance lags, the plan calls for a temporary reduction. The withdrawal rate flexes with the portfolio instead of ignoring it.
Bengen's own thinking has moved in a similar direction. He now recommends retirees revisit their withdrawal rate every couple of years rather than setting it once and never touching it again. The rule was never meant to be static, but retirees didn’t have the tools to make it dynamic.
What One-Size-Fits-All Can Cost Retirees
A fixed percentage doesn't account for sequence of returns risk, the outsized damage a market downturn can do when it hits in the first few years of retirement, nor does it account for the fact that spending patterns shift over the course of retirement, often declining in the middle years before rising again as healthcare costs increase later in life.
It treats every retiree's portfolio, risk tolerance, and income need as interchangeable, when every retirement plan calls for customization.
The Evolution of Retirement Income Planning
Modern retirement income planning starts with determining what each client’s spending needs look like year after year and builds a structure to fund those needs directly. Income-driven portfolio construction, matched to a retiree's real timeline and real expenses, replaces a single static assumption with a plan that adjusts as circumstances change.
The 4% rule gave retirees and advisors a starting point when almost nothing else existed. Three decades of research later, it's time to build on it.
Explore how income-first planning gives retirees a strategy built for how they spend.