If you think it’s hard saving for retirement as a couple, trying doing it as a single. According to a study—described by one expert as the most intriguing of 2012—the amount of money singles in their late 60s have saved up for retirement is dramatically less than that of married-couple households.

In fact, the median married household had in 2008 nearly 10 times more saved up for retirement than the median single-person household, $111,600 vs. $12,500. (Savings, for the record, included 401(k)s and IRAs and all taxable savings and investment accounts, but it did not include Social Security, pensions, or housing wealth. And single, at least for the purpose of this research could mean divorced, widowed or unmarried for most/all of their life.)

The difference was also extreme at the extremes, according to a blog post by Steve Utkus, who oversees the Vanguard Center for Retirement Research.

In his review of the study, Utkus noted that the top 30% of married households had savings of $332,400 or more while the top 30% of single-person households had just $90,000 or more. The bottom 30% of married households, meanwhile, had less than $24,000 saved while the bottom 30% of single-person households had less than $800.

The paper, from the National Bureau of Economic Research, is titled “The composition and drawdown of wealth in retirement,” and is co-written by James Poterba, Steven Venti and David Wise. Read Utkus’ blog, Retirement: The married/single divide.

Why the sharp divide?

So what’s going on? What explains this sharp divide?

According to Utkus, divorce is one reason why older single households have less money. When a couple separates, assets are divided, and savings can fall due to legal and other costs.

But divorce isn’t the main reason for singles having less money. If that were the case, Utkus wrote, he’d expect single-person figures to be just under half of those for married couples. But the gap is much wider than that. To be fair, the study doesn’t reflect the value of housing wealth which often becomes part of a divorce settlement, so it’s possible that the gap is not as wide.

The early death of a spouse is another reason why single households have less money than married households, according to Utkus. The all-too-familiar situation goes something like this: “One spouse, often the working male, becomes sick in his 50s or early 60s, loses work, and then dies prematurely,” he wrote. “The healthier spouse, often the female, may have a lower income or may not be working. She spends savings on living expenses and her husband’s medical costs. The loss of savings accelerates if they lose health insurance. Long-term care such as a nursing home can also accelerate the loss of assets. Medicaid, which can be used to pay for nursing care, doesn’t kick in until the household depletes most of its savings.”

And being single for most if not all of one’s life is yet another reason why single households have less money than married households. “When you live alone, you don’t benefit from the economies of scale of sharing costs with another person in the household, and so you may save less over your lifetime for a given level of income,” Utkus wrote. “If you lose your job, you don’t have the self-insurance that comes from having another household member with income and health benefits.”

So what lessons can be drawn from the findings? In general, if you’re single you’ll need to accumulate much more in your nest egg than your married counterparts, according to Utkus.

Plus, you need to make sure you have the right kinds of insurance in place. “You need also to protect against large, unexpected claims,” he wrote. And that means, having disability, life, and health insurance. “The new health care act may help when you lose workplace coverage—but of course you’ll still need to buy a policy,” he wrote.

But what one does to counteract the risks of being single depends also on the nature of the household.

Single for life

For instance, Utkus said, those who are single/unmarried for life tend to underestimate the amount of savings they need while those who are married/partnered tend to save more because they are saving for two rather than one.

“This, I believe, is still conjecture, but if it is true, it suggests that those not married need to make a special effort to save more than they might otherwise believe,” Utkus said. “Singles need to be aware that they are in a riskier position. There’s not second-income potential in the household, no sharing of living expenses. So they should be aggressive savers.”

Changes in marital status: divorce

As for those who are either divorced or want to protect against the risks associated with being divorced, Utkus had this advice: “Divorce can set back a retirement plan,” he said.

It raises cost of living (two live more cheaply together than on their own), and it reduces savings because of fees, such as lawyer expenses).

“Those getting divorced, particularly later in life, should do so with their eyes wide open,” he said. It’s best, he said, not just to consult a lawyer but also talk with a financial planner about the post-divorce financial situation. Among the things to address is whether and how to divide assets.

For the record, the Society of Actuaries (SOA) has published a guide to help you address some of the risks in retirement, including changes in marital status and becoming a widow or widower.

According to the SOA, divorce is a personal issue and there are no formal risk-management programs. But there are some things to consider. “At divorce, the law allows for split of private pension plan benefits covered by ERISA,” the SOA writes in its guide. “For this purpose, divorcing spouses need a properly drafted qualified domestic relations order (QDRO).”

And older couples who marry, especially those with children, may want a prenuptial agreement that defines each party’s rights to distribute or dispose of property as they wish, not as a court would decree, the SOA wrote.

The death of a spouse

Coming up with ways to protect against the risk of becoming a widow or widower requires more research, according to Utkus. “One of the unanswered questions in this area is the number of single-person households which arise due to death of a spouse and depletion of assets—either on health costs that are uninsured or on long-term care costs, such as nursing care or nursing-home care not covered by personal savings,” he said. “I think we need to know more about this area is clear. But if it is long-term care, it’s a complex issue.”

Study: Couples are more successful in saving

According to the SOA guide, it’s very difficult to predict which spouse will live longer in individual cases. But on average, women are widowed more often than men. And when that happens, there’s typically a decline in economic status. The SOA suggests that many financial vehicles can be used in combination to manage the death-of-spouse risk. Those include life insurance; survivor income in Social Security, pension plans and annuities, long-term care insurance, and savings. Wills and estate planning are important tools to provide for a surviving spouse. And a well-structured retirement-income plan can be an important source of stability for the surviving spouse. Read “Managing Post-Retirement Risks.”

Read related column, “True love means planning ahead.” That column detailed 10 ways husbands could help their wives survive widowhood.

Utkus said: “In many studies of retirement preparedness, getting divorced, becoming a widow or widower, or being single are risk factors associated with being financially unprepared for retirement. This important study (from Poterba, Venti, and Wise) reminds us why—and also suggests how, as individuals, we might counteract some of these risks.”

Robert Powell is a featured writer on the MarketWatch Retirement blog, a Research Fellow at the California Institute of Finance, and  a Featured Contributor here on the CIF blog.