Comprehensive Overview: The 4% Rule (EP.164)

Episode Summary

Executive Summary: In this episode, Benjamin Felix and Cameron Passmore assemble expert clips to explain the 4% rule: withdrawing 4% of a portfolio in year one and then adjusting that dollar amount for inflation. They review its historical assumptions and limitations—including time horizon, country, taxes, costs, and market conditions—and argue that flexible spending plans are generally more realistic than a fixed inflation-adjusted withdrawal.

Main Topics: Origins and mechanics of the 4% rule: Bill Bengen’s original research tested inflation-adjusted withdrawals from a portfolio of U.S. large-cap stocks and intermediate-term Treasury bonds. A 4% initial withdrawal survived every historical 30-year period examined; the rule holds the dollar withdrawal path steady in real terms regardless of subsequent market performance. Limits of the historical evidence: The rule depends on U.S.-centered historical returns, a 30-year retirement, low investment costs, specific asset allocations, and disciplined behavior. International research, longer retirements, taxes, and today’s return expectations can all change the outcome. International and longer-horizon findings: Wade Pfau reports that the 4% rate worked historically in only the U.S., Canada, and New Zealand among the countries examined, and that a lower rate was needed for broader international success. Longer withdrawal periods also reduce success rates, a particular concern for early retirees. Flexible retirement spending: Moshe Milevsky and Michael Kitces argue that spending should respond to circumstances rather than remain fixed regardless of portfolio changes. Alternatives discussed include conservative spending with future raises, guardrails that trigger raises or cuts, and small permanent adjustments such as forgoing an inflation increase. The rule as a guideline rather than a guarantee: Scott Rieckens describes the 4% rule as a useful planning guideline, not a hard-and-fast promise. It can help people frame retirement goals while allowing for diversified income sources, ongoing work or business activity, and reassessment. Portfolio composition and market conditions: Bengen discusses higher historical withdrawal estimates after adding small-cap stocks, while noting their severe volatility and practical limits. He also describes how historical withdrawal outcomes varied with valuations and inflation, while the hosts caution that such hindsight-based results do not guarantee future outcomes.

Key Arguments: The 4% rule is a specific historical rule: withdraw 4% of the initial portfolio in year one, then increase that dollar amount with inflation. It is not the same as withdrawing 4% of the portfolio’s changing balance each year. A historical success in U.S. data is not a universal guarantee. Pfau’s international analysis found that the 4% rule worked in only three of 20 countries studied and that the pooled international success rate was substantially lower. A longer retirement horizon makes a fixed withdrawal plan riskier; early retirees should not assume a rule tested for 30 years automatically applies to 40 years or more. The rule omits or simplifies important real-world factors, including taxes, fees, investor behavior, asset allocation, and the possibility of lower future returns. Fixed, inflation-adjusted withdrawals can be impractical because they do not respond to portfolio gains or losses. Flexible spending strategies can manage risk while avoiding constant, disruptive lifestyle changes. Guardrails can set thresholds for spending increases or cuts, while small permanent reductions—such as skipping an inflation adjustment—may support portfolio longevity more effectively than large, temporary cuts. Small-cap stocks raised historical withdrawal estimates in some analyses, but their extreme volatility and limited capacity make an all-small-cap strategy difficult for many retirees to tolerate or implement. The 4% rule can still be useful as a simple planning heuristic that encourages saving and realistic expectations, but the hosts suggest that a prudent estimate may often be below 4% and should depend on individual circumstances.

Data Points: Original 4% rule withdrawal: 4% of the initial portfolio in year one, then inflation-adjusted withdrawals - Bengen’s original analysis tested a 30-year retirement using U.S. large-cap stocks and intermediate-term Treasuries. Original portfolio allocation: Approximately 50% stocks and 50% bonds - The allocation associated with Bengen’s original 30-year analysis. Withdrawal-period test range: Starting years from 1926 to 1976 - The hosts describe testing 30-year withdrawal periods beginning in each of these calendar years. Success rate for a 40-year period: About 87% - The hosts say the original 4% approach’s historical success rate falls from its 30-year result when extended to 40 years. Countries where the 4% rule worked in Pfau’s study: 3 of 20: the United States, Canada, and New Zealand - Pfau compared historical outcomes across 20 countries. International success at a 4% withdrawal rate: About 68% - Pfau’s pooled international analysis used a 50/50 allocation. International rate for 90% success: 2.8% - Pfau’s estimate for a withdrawal rate that worked 90% of the time across the international data. Bengen’s later withdrawal estimate: About 4.5% - Bengen says adding U.S. small-cap stocks to the asset mix increased the historical estimate from roughly 4.1–4.2% to nearly 4.5%. Bengen’s 50-year comparison: 3.6% for U.S. small-cap value versus 3.1% for the U.S. total stock market - The hosts cite their own historical analysis of safe withdrawal rates. Illustrative guardrail thresholds: A 5% starting withdrawal, a raise if the rate falls below 4%, and a cut if it rises to 6% - Kitces gives a hypothetical guardrail example, including a 10% adjustment at the thresholds. Inflation adjustment example: A 2.7% inflation increase would raise a $10,000 monthly distribution to $10,270 - Kitces uses this to illustrate how inflation adjustments may work in practice. Small-cap volatility examples: Some years down 65–70%; other years up 150% - Bengen cites the volatility as a reason retirees may find an all-small-cap allocation difficult to tolerate.

Pivotal Quotes: "The idea of picking a spending rate at the age of 65 and sticking to that spending rate for the rest of your life, no matter what happens, I mean, it is ridiculous." — Moshe Milevsky: He argues that retirement spending should adapt to market and portfolio conditions rather than follow a rigid, lifelong amount. "I think the 4% rule is really more of a 4% guideline. Rule is probably the wrong word." — Scott Rieckens: He characterizes the rule as a useful planning frame, not a guarantee—particularly relevant to early retirement. "the 4% rule is not a rule of nature, it's just a rule of thumb, experiential rule" — Bill Bengen: He acknowledges that the estimate comes from historical experience and can change with future conditions.

Implications: Use the 4% rule as a starting point, not a promise. Retirement plans should account for horizon, taxes, fees, asset mix and uncertainty, and consider flexible spending thresholds that can adapt without forcing constant lifestyle changes.