The 4% rule suggests that retirees can withdraw 4% of their retirement savings in the first year of retirement and then adjust that amount for inflation each subsequent year. This approach aims to provide a steady income stream while preserving the longevity of the retirement portfolio.

For example, if you have $1 million saved for retirement, you would withdraw $40,000 in your first year of retirement. If inflation is 2% the following year, you would increase your withdrawal to $40,800.

The rationale behind the 4% rule

Bengen's research, often referred to as the Trinity Study, analyzed historical data on stock and bond returns over a 30-year retirement period. He concluded that a 4% initial withdrawal rate, followed by inflation-adjusted withdrawals, would have sustained a retiree’s portfolio through most historical periods. The rule assumes a diversified portfolio with a mix of stocks and bonds, typically 50% to 75% in stocks and the rest in bonds.

Application of the 4% rule

1. Initial calculation: Calculate 4% of your total retirement savings to determine your first year's withdrawal amount. This sets the baseline for your retirement income.
2. Adjusting for inflation: Each year, increase the previous year's withdrawal amount by the inflation rate to maintain purchasing power. This adjustment helps protect against the erosion of your income's value due to rising costs.
3. Portfolio management: Maintain a balanced portfolio of stocks and bonds to align with the historical data used in the rule’s formulation. Regular rebalancing ensures that your portfolio remains aligned with your risk tolerance and investment goals.

Benefits of the 4% rule

• Simplicity: The rule is easy to understand and implement, providing a straightforward guideline for retirement withdrawals.
• Sustainability: Historically, the 4% rule has been shown to support a 30-year retirement period, making it suitable for most retirees.

Limitations and considerations

• Market conditions: The 4% rule is based on historical data. Future market conditions could be different, potentially affecting the rule's reliability.
• Inflation rates: The rule assumes a relatively stable inflation rate. Periods of high inflation could challenge the sustainability of the 4% withdrawal rate.
• Longevity: Retirees living significantly longer than 30 years may need to adjust their withdrawal strategy to ensure their savings last.
• Flexibility: The rule does not account for changes in spending needs. Retirees might spend more in early retirement and less later, requiring a more dynamic withdrawal strategy.

The 4% rule provides a helpful framework for retirees planning their withdrawal strategy. While it offers a solid starting point, it’s important to consider individual circumstances, market conditions and potential adjustments. Consulting with a financial advisor can help tailor the 4% rule to your specific needs, ensuring a more secure and sustainable retirement.