Safe Withdrawal Rate (SWR) Method: Calculations and Limitations

What Is the Safe Withdrawal Rate (SWR) Method?

The safe withdrawal rate (SWR) method is one way that retirees can determine how much money they can withdraw from their accounts each year without running out of money before reaching the end of their lives.

The safe withdrawal rate method is a conservative approach that tries to balance having enough money to live comfortably with not depleting retirement savings prematurely. It is based largely on the portfolio’s value at the beginning of retirement.

Key Takeaways

  • The safe withdrawal rate (SWR) method calculates how much a retiree can draw annually from their accumulated assets without running out of money prior to death.
  • The SWR method employs conservative assumptions, including spending needs, the rate of inflation, and how much annual return investments will return.
  • One problem with SWR is that it projects economic and financial conditions at retirement to continue as-is into the future, when in fact they can change in the years or decades after retirement.

How Much Should Retirees Withdraw From Accounts?

Understanding the Safe Withdrawal Rate (SWR) Method

Figuring out how to use your retirement savings isn’t easy because there are so many unknowns, including how the market will perform, how high inflation will be, whether you will develop additional expenses (such as medical), and your life expectancy. The longer you expect to live, the longer the time period you need to cover, which means you may experience more "unknowns" or factors that you can't control. In addition, the worse the market performs, the more likely you are to run out of money.

The safe withdrawal rate method tries to prevent these worst-case scenarios from happening by instructing retirees to take out only a small percentage of their portfolio each year, typically 3% to 4%. Financial experts recommended safe withdrawal rates have changed over the years as experience has illustrated what really works and what doesn’t work and why.

Knowing what safe withdrawal rate you’d like to use in retirement also informs how much you need to save during your working years. If you want to withdraw more money per year, then clearly, you'll need to have more money saved. However, the amount of money you might need to live on might change throughout your retirement. For example, you might want to travel in the early years and, therefore, would likely spend more money versus the later years. As a result, your safe withdrawal rate could be structured so that you would withdraw 4%, for example, in the early years and 3% in the later years.

The 4% rule is a guideline used as a safe withdrawal rate, particularly in early retirement, to help prevent retirees from running out of money.

How to Calculate the Safe Withdrawal Rate

The safe withdrawal rate helps you determine a minimum amount to withdraw in retirement to cover your basic need expenses, such as rent, electricity, and food. As a rule of thumb, many retirees use 4% as their safe withdrawal rate—called the 4% rule

The 4% rule states that you withdraw no more than 4% of your starting balance each year in retirement. However, the 4% rule doesn't guarantee you won't run out of money, but it does help your portfolio withstand market downturns, by limiting how much is withdrawn. In this way, you have a much better chance of not running out of money in retirement.

Although there are a few ways to calculate your safest withdrawal rate, the formula below is a good start:

  • Safe withdrawal rate = annual withdrawal amount ÷ total amount saved

Let’s say as an example, you have $800,000 saved and you believe you’ll need to withdraw $35,000 per year in retirement. The safe withdrawal rate would be: 

  • $35,000 ÷ $800,000 = 0.043 or 4.3% (or .043 * 100)

If you believe you'll need a higher or lower amount of income in retirement, here are a few examples:

  • $25,000 ÷ $800,000 = 0.031 or 3.0% (or .03 * 100)
  • $45,000 ÷ $800,000 = 0.056 or 5.6% (or .056 * 100)

So, if you only needed $25,000 per year in withdrawals, you could safely withdraw it since it would only be 3% of your balance each year.

If you believe you would need $45,000 per year in retirement and you want to only withdraw 4% of your retirement balance, you would need to save more money. In other words, $45,000 per year in withdrawals from a balance of $800,000 would yield a 5.6% withdrawal rate, which might lead you to run out of money.

To calculate how much in retirement funds you'd need to satisfy the 4% rule and be able to safely withdraw $45,000 per year, we would rearrange the formula as follows:

  • Annual withdrawal amount ÷ safe withdrawal rate = total amount saved
  • $45,000 ÷ 0.040 = $1,125,0000

Now you know that you would need to save an additional $325,000 beyond your current balance of $800,000 to be able to satisfy the 4% rule and withdraw $45,000 per year safely. If you lower your withdrawal rate–all else being constant—your funds will last longer. However, if you want a higher withdrawal rate, you'll need to be sure that there will be enough funds to last 20 to 30 years since you might run the risk of depleting your funds.

Limitations of the Safe Withdrawal Rate Method

A shortcoming of the safe withdrawal rate method is that depending on when you retire, the economic conditions can be very different from what initial retirement models assume. A 4% withdrawal rate may be safe for one retiree yet cause another to run out of money prematurely, depending on factors such as asset allocation and investment returns during retirement.

In addition, retirees don’t want to be overly conservative in choosing a safe withdrawal rate because that will mean living on less than necessary during retirement when it would have been possible to enjoy a higher standard of living. Ideally, though this is rarely possible because of all the unpredictable factors involved, a safe withdrawal rate means having exactly $0 when you die, or if you want to leave an inheritance, having exactly the sum you want to bequeath.

Alternatives to the Safe Withdrawal Rate Method

People often make the mistake in retirement that they continue spending too much even at times when their portfolio is down. This behavior can increase the possibility of failure (POF) rate, or the percentage of simulated portfolios that fail to last to the end of a person's expected retirement.

An alternative to the safe withdrawal rate method is dynamic updating—a method that, in addition to considering projected longevity and market performance, factors in the income you might receive after retirement and reevaluates how much you can withdraw each year based on changes in inflation and portfolio values.

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