Carla Fried: What’s your retirement number? No, not savings – life expectancy

American males born today have an average life expectancy of 76 years, and females 81 years. That means that half of males born today will still be alive at age 76 and half of females will still be alive at 81.

But those are lousy numbers for retirement planning. You want to focus on the probabilities of living to a certain age assuming you make it to 65 in the first place.

The Society of Actuaries is the go-to resource. According to the SOA, a 65-year-old male today, in average health, has a 55% probability of living to age 85. For a 65-year-old woman, the probability of reaching 85 is 65%.

Age 90 isn't some wild outlier. The SOA's data suggests that a 65-year-old male today, in average health, has a 35% chance of living to 90; for a woman the odds are 46%. If our two 65-year-olds live together, there is a 50% chance both will still be alive 16 years later, and that one will survive 27 years.

That's just assuming average health. Suppose you have a wonderful gene pool and are committed to healthful habits. According to the SOA, a non-smoking, 65-year-old male in excellent health today has a 43% probability of living to age 90, and a similar 65-year-old female has a 54% probability of living to 90. One-third of today's 65-year-old women in excellent health and about one in four men are expected to be alive at 95.

The SOA has a terrific free longevity calculator where you can plug in your age and general health condition to get a clear-eyed estimate of how long you'll likely need your retirement plan to support you. The tool also spits out probabilities other than 50%. If you want to be extra cautious, you can use estimates based on 25% or 10% probabilities of living to a certain age.

HOW TO PLAN FOR A POTENTIALLY VERY LONG LIFE

While how much you manage to save for retirement by a certain date obviously is important, what tends to get less attention is your longevity. What you save is just one part of the equation. The other part: How long do you need that pot of money to last?

Any financial advisor with chops will crunch your numbers assuming you live to 95. Some will even stretch that out to 100. If you find yourself noodling with an online retirement income calculator that asks you how long you expect to live, consider plugging in at least 90 or 95 if you're in good health today.

HOW TO REVISE YOUR CURRENT RETIREMENT PLAN FOR A VERY LONG LIFE

--Save more. Sure, you want to have a smart mix of stocks and bonds based on your age and risk tolerance, but there's no allocation in the world that works if you don't save enough in the first place.

--Plan to work a little longer. Delaying retirement a year or two or three can do wonders for income security. It gives your savings a few more years to compound and reduces the number of years you need to rely on savings. That doesn't necessarily mean sticking with your age-50 career job until age 70. That may not be appealing or practical, given the vulnerability older workers have in today's job market. A job that covers your essential living costs may be all you need to delay starting to take money out of your retirement accounts.

--Start Social Security payouts at age 70. Take your benefit at 62 and it will be 30% smaller if your full-retirement age is age 67. If you wait until age 70, you will earn 8% for each year after age 67; that's another 24% income boost over your FRA benefit.

If you are married, it's most important for the highest earner to delay until age 70. It's less important when the other spouse starts.

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