If retirement planning had a soundtrack, a great candidate would be "Love and Marriage," the old Sammy Cahn / Jimmy Van Heusen song made famous by Frank Sinatra.

So much planning advice focuses on married couples -- think Social Security spousal benefits, joint and survivor pensions, or beneficiary rights for 401(k) and IRA accounts. But how about retired singles? Their numbers will be increasing in the years ahead -- about one third of adults ages 46 through 64 were divorced, separated or had never been married in 2010, compared with 13 percent in 1970, according to demographers at Bowling Green State University in Ohio. And they will face tougher challenges achieving a secure retirement than married people.

Living expenses are higher as a proportion of income -- the cost of shared housing, food, utilities, and transportation are easier to manage when spread over two income streams. Single people also can't take advantage of the tax breaks available to joint-filing married couples.

"There certainly are economies of scale for married people," says Catherine Collinson, president of the Transamerica Center for Retirement Studies.

Single women have an especially steep hill to climb. They tend to outlive men, which means they need to stretch retirement savings further. Yet they earn less than men; the median pay for a woman in 2013 was $39,157, just 78 percent of the median $50,033 earned by men, according to U.S. Census Bureau data.

"Women do earn less than men, and that means they need to plan more aggressively for retirement," says Manisha Thakor, CEO of MoneyZen Wealth, an independent advisory firm specializing in planning for women.

advertisement | advertise on newsday

Collinson's organization has studied the retirement gender and marriage gaps, and the numbers aren't encouraging. Consider the following responses by workers age 50 and older to a Transamerica survey:

* 52 percent of single women expect Social Security to be their primary income source in retirement, compared with 38 percent of single men; 48 percent of single women expect their standard of living to decline in retirement, compared with 39 percent of men.

* 56 percent of single women expect to work past age 70 or to never retire, compared with 51 percent of single men. The numbers are far lower for married people -- 39 percent of women and 46 percent among men.

* Single women have median retirement savings of just $35,000, compared with $70,000 for single men.

Experts offer the following suggestions on how to flip these figures.

Best Bets

Get the scoop on events, nightlife, day trips, family fun and things to do on Long Island.

HAVE A PLAN Transamerica's survey research shows that married couples tend to be more engaged in planning for retirement: 74 percent of married workers describe themselves as "very involved in monitoring and managing their retirement savings," compared with 62 percent of unmarried workers.

FOCUS ON GUARANTEED INCOME For women, greater longevity offers good reasons to focus on maximizing guaranteed income from Social Security and defined-benefit pensions.

Never-married singles can boost Social Security income through a delayed-filing strategy. That's not to say filing early is never the right move -- it makes sense if you're in poor health or have a dire need for the income and can't work or draw on savings. But more often than not, women will come out ahead waiting at least until their full retirement age (currently 66), or closer to 70, the last age when additional credits are available.

"When I'm talking with women about their plans, I always tell them that they have to give me a good reason not to delay filing," Thakor says.

WEAVE A HEALTHCARE SAFETY NET Single people without kids may lack a natural support network in a health emergency -- so take the time to build one. "Thinking proactively to build out your network of friends and family can be very important," Thakor says. "Talk with your other single friends about creating a community to help one another out if something hits."

advertisement | advertise on newsday

Finally, take the time to understand your Medicare insurance selections, and consider whether you'll want to purchase long-term care insurance. If so, buy it at younger ages while you're still in good health, since insurers have been tightening their underwriting standards.