The 4% Rule Explained: Is It Still Valid in 2025?

Where the 4% Rule Comes From

In 1994, financial planner William Bengen published a landmark paper in the Journal of Financial Planning. Using historical U.S. stock and bond returns from 1926 through 1992, he analyzed what withdrawal rate a retiree could sustain across every 30-year period in that dataset. His conclusion: a withdrawal rate of 4% of the initial portfolio, adjusted annually for inflation, survived every historical 30-year period when the portfolio held at least 50% equities.

A few years later, three professors at Trinity University expanded on this work in what became known as the Trinity Study. They tested multiple withdrawal rates (3% through 12%) and multiple portfolio allocations across rolling 15-, 20-, 25-, and 30-year periods. At 4%, a 50/50 stock-bond portfolio succeeded in 95% of 30-year periods. The "4% rule" entered the financial planning lexicon.

What the 4% Rule Actually Says

The rule is often misquoted. Here is precisely what it claims:

• Withdraw 4% of your initial portfolio value in year one.
• Adjust that dollar amount by CPI inflation each subsequent year.
• Do this regardless of what the market does — no flexibility, no adjustments.
• Over a 30-year retirement, this approach historically survived in nearly every market environment, including the Great Depression and the 1970s stagflation.

A $1,000,000 portfolio would produce a $40,000 first-year withdrawal. If inflation runs 3%, the year-two withdrawal would be $41,200 — and so on, regardless of portfolio performance.

The Criticisms: Is 4% Still Safe?

1. Longer Retirement Horizons

The original research was based on 30-year retirements. Someone who retires at 55 may need their money to last 40 or even 45 years. Research by Wade Pfau and others suggests that over 40-year periods, a 4% withdrawal rate has historically failed in a meaningful minority of scenarios. For long retirements, a 3.5% or even 3.3% rate may be more appropriate.

2. Today's Starting Valuations

Historical success rates are averages across all starting points. But returns from any given period depend heavily on the valuation of equities at the start. When cyclically adjusted price-to-earnings ratios (CAPE) are elevated — as they have been through much of the 2020s — expected future real returns tend to be lower. Some researchers argue the safe withdrawal rate in today's environment may be closer to 3.3%–3.5%.

3. International Returns May Differ

The original Trinity Study used only U.S. market returns — one of the best- performing stock markets in history. A similar study applying the 4% rule to investors in other developed markets found much lower success rates, suggesting survivorship bias may make the U.S. historical record overly optimistic as a universal benchmark.

Dynamic Withdrawals: A Better Approach

The rigid 4% rule — withdraw the same inflation-adjusted dollar amount every year regardless of circumstances — is actually how almost no retiree behaves. In practice, retirees reduce spending when markets drop and may spend more in good years. Research shows that dynamic withdrawal strategies significantly outperform the rigid rule.

The Guardrails Method

Developed by Jonathan Guyton and William Klinger, the guardrails approach sets upper and lower boundaries on your withdrawal rate. If your withdrawal rate rises above a ceiling (e.g., 5.5%) due to a declining portfolio, you cut spending by 10%. If your rate drops below a floor (e.g., 3.5%) due to strong gains, you can spend 10% more. This flexibility allows for a higher starting withdrawal rate while maintaining long-term sustainability.

The Floor-and-Upside Method

Another approach separates essential spending (covered by guaranteed income sources like Social Security and annuities) from discretionary spending (funded by the investment portfolio). By securing essential expenses with guaranteed income, you reduce the withdrawal pressure on the portfolio and can tolerate more volatility.

What This Means for Your Plan

The 4% rule is not dead — it remains a useful baseline. But it should be treated as a starting point for analysis, not a guarantee. Here's a practical framework:

The bottom line: the 4% rule is a powerful heuristic that has held up remarkably well over time. Its real limitation isn't the number itself — it's treating that number as fixed rather than as a starting point for an adaptive, personalized retirement income strategy.