Understanding the 4% Rule
What is the 4% Rule?
The 4% rule is a retirement planning guideline that suggests withdrawing 4% of retirement savings in the first year, then adjusting that amount for inflation each year. Historical analysis shows how this approach performed over 30-year periods.
Practical Example
If you have $1,000,000 saved for retirement:
- Year 1: Withdraw $40,000 (4% of $1,000,000)
- Year 2: Withdraw $40,800 (previous year + 2% inflation)
- Year 3: Withdraw $41,616 (previous year + 2% inflation)
- And so on...
Source: The 4% rule was developed by financial planner William Bengen in 1994, based on historical analysis of U.S. stock and bond returns from 1926-1992. (Bengen, W. P. (1994). Determining withdrawal rates using historical data. Journal of Financial Planning, 7(4), 171-180.)
Key Concepts Explained
Withdrawal Rate
The percentage of your portfolio you withdraw each year. A 4% withdrawal rate means taking out 4% in year one, then adjusting for inflation.
Asset Allocation
How you divide your money between stocks and bonds. Stocks offer higher returns but more volatility; bonds provide stability but lower returns.
Success Rate
The percentage of historical 30-year periods where your money would have lasted. A 95% success rate means your plan worked in 95% of historical scenarios.
Sequence of Returns Risk
The risk that poor market returns early in retirement can permanently damage your portfolio, even if long-term returns are good.
How to Use This Analysis Tool
What it does: Shows how often different withdrawal rates would have failed (run out of money) in the past 94 years.
How to use it:
- Set your stock/bond allocation (60% stocks is a good starting point)
- Look at the chart to see failure rates for different withdrawal rates
- Choose a rate where you're comfortable with the failure risk
Example: At 60% stocks with inflation-adjusted withdrawals, a 4% withdrawal rate failed in 4% of historical periods, while 5% failed in 28%. With fixed dollar withdrawals 4% never failed - the toggle on each page lets you compare both.
What it does: Shows how different stock/bond mixes affect your success rate for a given withdrawal rate.
How to use it:
- Set your desired withdrawal rate (start with 4%)
- Look at the chart to see how success rates change with stock allocation
- Review the historical trade-offs between growth and stability
Example: For a 4% withdrawal rate, 60-70% stocks typically provides the highest success rates. Too few stocks = low growth; too many = high volatility.
What it does: Calculates the maximum withdrawal rate that would have exactly exhausted your portfolio in the worst historical 30-year period.
How to use it:
- Set your stock allocation
- See the "break-even rate" for the worst historical period
- Consider a withdrawal rate below this for an additional cushion
Example: At 60% stocks the worst-case break-even rate is 3.83% with inflation-adjusted withdrawals (a December 1965 retiree facing the 1970s stagflation). Choosing 3.5% would have provided a cushion even against the worst period in 94 years of history.
What it does: Shows how retirement length (25-50 years) affects the success of your withdrawal strategy.
How to use it:
- Set your withdrawal rate and stock allocation
- See how success rates change with retirement length
- Plan accordingly if you expect early retirement or long lifespan
Example: With inflation-adjusted withdrawals at 60% stocks, a 4% rate succeeded in 96% of 30-year periods but only 87% of 40-year periods. Early retirees often choose 3-3.5% for the additional margin.
Common Retirement Scenarios
Conservative Retiree
- Portfolio: $800,000
- Allocation: 50% stocks, 50% bonds
- Withdrawal Rate: 3.5%
- Annual Income: $28,000
Why this works: Lower withdrawal rate and conservative allocation provide high confidence but modest income.
Balanced Retiree
- Portfolio: $1,200,000
- Allocation: 60% stocks, 40% bonds
- Withdrawal Rate: 4%
- Annual Income: $48,000
Why this works: Classic 4% rule with balanced allocation provides good income with high historical success.
Early Retiree
- Portfolio: $1,500,000
- Allocation: 70% stocks, 30% bonds
- Withdrawal Rate: 3.25%
- Annual Income: $48,750
Why this works: Longer retirement needs lower withdrawal rate. Higher stocks offset lower rate with growth potential.
High-Income Retiree
- Portfolio: $2,000,000
- Allocation: 65% stocks, 35% bonds
- Withdrawal Rate: 4.3%
- Annual Income: $86,000
Why this works: Larger portfolio allows slightly higher withdrawal rate. Some flexibility to adjust if needed.
Important Limitations & Considerations
What This Analysis Does NOT Include
- Social Security: This tool assumes portfolio-only retirement income
- Pensions: Additional income sources change your withdrawal needs
- Healthcare Costs: Major medical expenses can impact sustainability
- Taxes: Assumes you're withdrawing from tax-advantaged accounts or have calculated after-tax amounts
- Fees: Returns are before fund fees and trading costs
- Future Market Performance: Based on historical data; future may differ
Recommendation: Consider this analysis as one tool among many. Consult with a financial advisor for personalized planning.
Data Sources & Methodology
Our analysis uses historical market data spanning 94 years (1928-2021) with monthly precision to test retirement strategies across 769 different 30-year periods, including:
- Major Market Crashes: Great Depression (1929), Oil Crisis (1973), Black Monday (1987), Dot-com Crash (2000), Financial Crisis (2008), COVID-19 (2020)
- Bull Markets: Post-WWII boom, 1980s-1990s expansion, recent recovery periods
- Various Economic Conditions: High inflation (1970s), deflation (1930s), varying interest rates
Data Sources:
- Stock Returns: S&P 500 monthly total returns (including dividends) from Robert Shiller's dataset
- Bond Returns: 10-year Treasury total returns derived from historical yields, and 3-month Treasury bills from Federal Reserve Economic Data (FRED)
- Inflation Data: Consumer Price Index (via Shiller's dataset). Inflation-adjusted withdrawals use each period's actual historical inflation - a 1966 retiree's withdrawals grow with 1970s inflation, not an average
Two withdrawal modes: Every analysis page lets you toggle between inflation-adjusted withdrawals (the classic 4% rule - spending keeps its purchasing power; 4% succeeded in 96% of periods at 60/40) and fixed dollar withdrawals (looks safer - 100% success at 4% - because spending shrinks in real terms over time).
A note on the 769 periods: the 30-year windows overlap (one starts each month), so they share data and are not 769 independent observations. See the methodology page for details.
Want to audit the math yourself? The step-by-step calculation walkthrough shows one complete trial month by month - every return, withdrawal, and balance - with a downloadable spreadsheet that reproduces the engine's arithmetic.
Academic Foundation: Methodology based on William Bengen's original research (1994) and subsequent studies by Trinity University researchers (1998), enhanced with monthly precision analysis for more realistic withdrawal modeling. Monthly data provides 11.8x more historical scenarios than annual analysis.