Until a few years ago, the Social Security Administration's website offered a calculator that let people figure how many years it would take to earn back benefits foregone by waiting to retire at a higher benefit rate.

That particular calculator was removed, says Social Security spokesperson Ben Stump, "because too many people were running the calculation, reckoning they might not live long enough to earn back the foregone benefits, and then taking earlier retirement at a lower benefit."

What's wrong with that? Well, as Stump points out, that web calculator ignored the importance of a higher benefit to a surviving spouse. As he notes, if the person in question is the higher earner in a couple and, as is most often the case, is also male, the actuarial odds are that his spouse will outlive him. And the higher his benefit amount, the higher the survivor benefit available to a surviving spouse. This could be important even if the higher earner is female, as it is a kind of insurance for the lower-earning spouse, male or female.

'NO BREAK-EVEN DISCUSSION'

Advisors need to make survivor benefits part of any client discussion about Social Security.

As Steven Williams, head of U.S. financial planning for BMO Private Bank, puts it, "For married couples, in the case of the higher earner there is no break-even discussion. If you're the higher-earning spouse, it's all about the survivor benefits."

Take the example of a 62-year-old man thinking of filing for Social Security -- the early option which is chosen by half of all retirees. Assuming a benefit of $750 per month at 62, if he waits until 70 to collect, his benefit (in constant dollars) will be about $1,320 per month, or 76% higher.

But choosing to receive that substantially higher benefit means he misses out on 96 months of benefits, or about $72,000. To earn all that missed money back, figuring in constant dollars, he'd have to live past 80. If he has health problems, he might figure he'll never make it.

Yet he's not single; he has a healthy spouse who could outlive him who has a lower Social Security benefit amount. Unless he factors in the importance of her being able to collect his maximum survivor benefit of $1,350 per month should she outlive him, he hasn't figured all the angles.

If he's not careful, he could unwittingly and unnecessarily leave her an impoverished widow.

Dave Lindorff spent five years as a China correspondent for Businessweek, and has written for The Nation and Salon.com.

This story is part of a 30-day series on Social Security and retirement income strategies.