To illustrate, if a retiree has a $100,000 portfolio, in the first year of retirement he should withdraw $4,000. Then $4,120 the next year ($4,000 plus an additional 3 percent for inflation), followed by $4,244 the year after that ($4,120 plus an extra 3 percent for inflation). And so on.
This strategy originated in 1994 with William Bengen, a financial planner from California. He determined this to be the ideal rate at which a portfolio of half large-cap stocks and half U.S. Treasuries can be drawn down to last 30 years. (In other words, long enough to survive nearly all retirements.)
But the times, as they say, are a-changin'.
According to a recent article published on CNBC.com, even Bengen himself "isn't convinced the rule still applies." He worries that artificially low interest rates and exaggerated stock market volatility could render his 4 percent rule outdated.
There's also uncertainty about future returns. If the stock market is not as lucrative in the next few decades as it has, on average, been for the past century, the 4 percent rule will be too aggressive. That's why some financial advisers are now recommending a 3 percent withdrawal rate.
Still others see both the 3 and 4 percent withdrawal rate recommendations as too conservative. According to a recent Wall Street Journal article, the amount of living expenses the 3 percent and 4 percent rules are based on might be "overestimating the real costs of retirement by as much as 20 percent." That's because, according to research from the Employee Benefit Research Institute, household expenses "steadily decline with age," falling 19 percent by age 75, 34 percent by 85, and 52 percent by 95. Which is why some experts are now saying that a retiree could safely withdraw even more than 5 percent a year.
The Right Withdrawal Rate for You
The 4 percent withdrawal rule is a good starting point for retirement planning. But you shouldn't just stop there. There are many variables at play in determining what works for you: A 3 percent withdrawal rate may be necessary for one retiree, while another might be able to sustain 5 percent withdrawals or higher.
To determine your best withdrawal rate takes some serious thought and calculating. Here are some things to keep in mind as you think through what your own scenario will be.
The 4 percent rule doesn't apply if you haven't saved enough. According to the National Institute on Retirement Security, the typical 55-to-64-year-old (folks nearing retirement) has only $12,000 in savings.
The numbers are dependent on your life expectancy. It's impossible to know exactly how much life you have left -- but if your family consists of centenarians, a lower withdrawal rate would be wise. The converse is true if none of your relatives have lived past 70. You want your money to last a little bit longer than you do. Making that happen may mean adjusting your withdrawal rate as you age.
Your ideal withdrawal rate depends heavily on your portfolio's growth rate. Conservative portfolios (those with more than 60 percent of the assets in bonds) can't grow as rapidly as aggressive portfolios (in which stocks make up the majority). Therefore, conservative investors should withdraw less -- while those able to stomach the volatility of being heavily in stocks could probably withdraw 5 percent or more each year -- if your stocks are doing well. But remember, past stock market performance is no guarantee of future performance. And you may have to adapt on the fly.
Your withdrawal rate should depend on the amount of money you need. It should be obvious, but don't pull cash out of your portfolio to spend just because of a guideline. If you need less than 4 percent or even less than 3 percent of your portfolio to cover those living expenses that Social Security does not, let the money stay invested and growing.
Start running different growth and withdrawal scenarios today. The sooner you do, the more time you'll have to adjust your plan for a comfortable retirement.
Motley Fool contributing writer Adam Wiederman has no position in any stocks mentioned.