How to Make Sure Your Money Lasts Through Your Retirement

The S&P 500 didn't gain ground in 2015, so neither did retiree Bruce Stanton's spending money. That summer, the former teacher in Washougal, Wash., dialed back what he withdrew from his retirement account to reflect the lackluster market. Fluctuations in income aren't that rare. During his career as a chemistry teacher, Stanton would sometimes get a big raise and other times get none. "I'm used to going without them," says Stanton, 63.

A challenge for all retirees is creating an income stream that will last a lifetime even if a downturn takes a big bite out of their savings. Some, like Stanton, are tackling this by adjusting withdrawals based on the market's performance.

But market-linked approaches run counter to the long-standing 4% rule, which holds that your money will last for a 30-year retirement if you withdraw 4% of your nest egg the first year and adjust that dollar amount annually for inflation.

Some experts are now arguing for a lower initial rate—such as 3%—since stocks and bonds may deliver below-average returns over the next few decades. Yet for much of history, 4% has been conservative, according to financial adviser Michael Kitces. 

So what's a retiree to do? As an alternative to withdrawing a fixed percentage, here's a look at four "dynamic" withdrawal strategies.

Skip rises in down years.

Under the 4% rule, retirees with $1 million would take out $40,000 in the first year. Then they'd typically boost that dollar amount in subsequent years based on the consumer price index (CPI), a common gauge of inflation. So if CPI rises 2%, they'd take out $40,800 in year two.

But to play it safer, you could choose to skip those raises in years following negative returns for your portfolio.

David Blanchett, Morningstar's head of retirement research, says if you skip the inflation bump in down years, the chances your money will last until age 90 will go up by nearly 11 percentage points, assuming an initial 4% withdrawal.

Ratchet higher in up years.

What if you care about flexibility, but instead of sacrificing after down years, you want to reap the rewards of a strong market?

Kitces says if your account ever grows 50% above its starting value after initiating withdrawals—says you retired with $1 million but your balance rises to $1.5 million—you can go ahead and boost your withdrawals by an additional 10% above any inflation adjustments in perpetuity. Assuming you were going to withdraw $45,000 this year, you'd actually be able to tap as much as $49,500. And you wouldn't have to slash withdrawals after subsequent downturns.

According to Kitces, this strategy won't deplete your account under any scenario. The higher spending, though, makes this less than ideal if you want to leave legacies to your heirs.

Set a floor and a ceiling.

This hybrid approach, pioneered by Vanguard, starts out by establishing an annual rate of withdrawals—say, 4%. Then you set a ceiling that's no more than 5% higher than the prior year's income level, and a floor that's no more than 2.5% lower.

Here's how that would work: Assume you start with $1 million, and say you plan to withdraw 4%, or $40,000, at year's end. But market forces boost the value of your nest egg by 20% to $1.2 million. How much would you be able to tap at the end of year two? Well, you'd start by applying that 4% rate again to your new balance, which comes to $48,000. Then you'd see if that amount falls within your ceiling and floor. In this case, a 5% ceiling on $40,000 would be $42,000, which is below the $48,000 mark—so you'd go with the lower figure.

This ceiling-and-floor approach had a 92% success rate, meaning in more than nine out of 10 possible scenarios, retirement funds aren't depleted even after 35 years, according to Vanguard. By contrast, the traditional 4% rule with annual inflation adjustments resulted in a 78% success rate.

This also mimics human behavior: People tend to splurge when the market is up, and dial back when it's down, says Francis Kinniry, a principal in Vanguard Investment Strategy Group.

Use RMDs as your guide.

Once you reach age 70½, you have to take required minimum distributions (RMDs) from your traditional IRAs. Its Uncle Sam's way of getting his hands on money that's been tax sheltered for years.

To calculate your RMD, you divide your IRA balance by an IRS-provided figure that represents an actuarial estimate of the remaining life span of someone your age. At 70, your denominator is 27.4; meaning that under certain circumstances someone your age may live until nearly 97½.

As it happens, you can "take advantage of the actuarial strategy behind RMDs to guide your spending," says Wade Pfau, professor of retirement income at the American College of Financial Services. No one under 70½ must take RMDs, but there are equivalent lifetime expectancy figures. For a 65 year old, it's 31.9.

If you retire at 65, you'd divide your nest egg by 31.9. With a $1 million account, that's $31,350, meaning rather than tapping 4% of your nest egg, you'd be taking 3.1%, a relatively conservative approach.

Investors who aren't looking to leave a lot in their accounts for heirs might alter the formula slightly to boost their income.

For instance, you might modify your RMD amount by a factor of 1.1. Here, you'd multiply that $31,350 figure by 1.1, and at 65 you could withdraw close to $34,500 on that $1 million account.