TIME Diet/Nutrition

Soda May Age You as Much as Smoking, Study Says

The link between soda and telomere length

Nobody would mistake sugary soda for a health food, but a new study published in the American Journal of Public Health just found that a daily soda habit can age your immune cells almost two years.

Senior study author Elissa Epel, PhD, professor of psychiatry at University of California San Francisco, wanted to look at the mechanisms behind soda’s storied link to conditions like diabetes, heart attack, obesity, and even higher rates of death. She studied telomeres, the caps at the end of chromosomes in every cell in our body, from white blood cells. Shorter telomeres have been linked to health detriments like shorter lifespans and more stress, cardiovascular disease, diabetes and cancer, the study notes.

Epel and her team analyzed data from 5,309 adults in the National Health and Nutrition Examination Survey (NHANES) from about 14 years ago. They found that people who drank more sugary soda tended to have shorter telomeres. Drinking an 8-ounce daily serving of soda corresponded to 1.9 years of additional aging, and drinking a daily 20-ounce serving was linked to 4.6 more years of aging. The latter, the authors point out, is exactly the same association found between telomere length and smoking.

Only the sugary, bubbly stuff showed this effect. Epel didn’t see any association between telomere length and diet soda intake. “The extremely high dose of sugar that we can put into our body within seconds by drinking sugared beverages is uniquely toxic to metabolism,” she says.

She also didn’t see a significant link between non-carbonated sugary beverages, like fruit juice, which Epel says surprised her. But she thinks the results might be different if the data were more modern. “We think that the jury’s still out on sugared beverages—theoretically they’re just as bad,” she says. “But 14 years ago people were drinking a lot less sugared beverages…they were mostly drinking soda.” At the time of the study, 21% of adults in the study reported consuming 20 ounces or more of sugar-sweetened soda each day, but soda consumption has been on the decline for years.

Telomere length dwindles naturally as we age, but it may not be an irreversible process. Previous research shows that it’s possible to increase telomere length by as much as 10% over 5 years by stressing less and eating a healthy diet—no soda included.

Read next: Here’s How to Stop Teens From Drinking Soda

TIME Aging

How to Talk About The End of Your Life

The toughest conversation might also be the most important

The video of Brittany Maynard, 29, describing her choice to move to Oregon for the right to end her life due to her terminal cancer has received well over 7 million views. It’s also left many people shocked, saddened and inspired by her decision.

“I am not suicidal. If I were, I would have consumed that medication long ago. I do not want to die. But I am dying. And I want to die on my own terms,” Maynard wrote on CNN.com.

Talking about death—and the circumstances surrounding it—is uncomfortable for most people. But my colleague Lily Rothman, 28, just wrote her will. “My eventual death was something I’d been mentioning to lots of people, on Facebook and at engagement parties and at my high-school reunion,” she writes. “It wasn’t that I thought death was going to come any time soon or in any special way, it’s just that, as they say on Game of Thrones, all men must die.”

MORE: 5 Tips For Families Facing End-Of-Life Care

Many people argue that it’s time we had more conversations about the end of life and how we want to go. It’s a conversation that can become awkward, especially for adult children bringing it up to their parents, but it allows people to avoid having to make very difficult decisions at the most sensitive times. “It’s critically important for us to have these conversations at the kitchen table,” says Ellen Goodman, founder of The Conversation Project, a nonprofit organization that campaigns for the expression and respect of wishes for end-of-life care. “Too many people are not dying in the way that they choose, and we need to change that.”

Goodman, who had to make medical decisions for her dying mother that they had never discussed beforehand, also created the Conversation Starter Kit, which you can download for free. So far, people in 50 states and 176 countries have downloaded the kit. That’s great news, considering about 90% of Americans believe it’s important to talk about their end-of-life care wishes and those of their loved ones, but only 30% actually have those discussions, according to the Conversation Project. “We would hope that this really tragic story of [Brittany Maynard] has an outcome that will really help people talk about these issues,” says Goodman.

Here are some other preparations you might consider if preparing an end-of-life checklist, from the National Institute on Aging:

  • A living will, which records a person’s wishes for medical treatment near the end of life.
  • Designating a durable power of attorney for health care, which names a person, sometimes called an agent or proxy, to make health care decisions when a person can no longer do so.
  • Talking about a do-not-resuscitate (DNR) order, which instructs health care professionals not to perform cardiopulmonary resuscitation if a person’s heart stops or if he or she stops breathing. A DNR order is signed by a doctor and put in a person’s medical chart.
  • Writing a will—a document that indicates how a person’s assets and estate will be distributed upon death.
  • Naming a durable power of attorney for finances, someone to make financial decisions when the person no longer can. It can help terminally ill people and their families avoid court actions that may take away control of financial affairs.
  • Penning a living trust, which provides instructions about the person’s estate and appoints someone, often referred to as the trustee, to hold the title to property and funds for the beneficiaries. The trustee follows these instructions after the person can no longer manage his or her affairs.
TIME Aging

5 Reasons Why Women Live Longer Than Men

Pink stethoscope with female symbol
Getty Images

Life expectancy in the U.S. is at an all-time high, according to a recent report by the Centers for Disease Control and Prevention (CDC). And while the news that we’re living, on average, to the ripe old age of 78 years and 9 ½ months isn’t that surprising, there is one stat that is: A girl born in 2012 can expect to live to 81.2 years—almost 5 years longer than a boy baby born the same year, who’s likely live to age 76.4. Weaker sex, indeed.

“Men are biologically and sociologically at a disadvantage from the time they’re conceived to the time they die,” says Marianne Legato, MD, professor emerita of clinical medicine at Columbia University College of Physicians and Surgeons and founder and director of the Foundation for Gender-Specific Medicine. Here’s why:

Females are tougher in utero

Two and a half as many boys are conceived as girls, Dr. Legato says, but they’re so much more likely to succumb to prenatal infection or other issues in the womb that by the time they’re born, the ratio is close to one to one. “They’re also slower to develop physically than girls prenatally, which means they’re more likely to die if they are preemies due to underdeveloped lung or brain development,” Dr. Legato explains.

HEALTH.COM: 10 Biggest Myths About the Flu

Women are less likely to be daredevils

Unintentional injuries are the third leading cause of death in men, according to the CDC; for women it’s only the sixth. Again, you can blame it on biology: The frontal lobes of the brain—which deal with responsibility and risk calculation—develop much more slowly in males than females, Dr. Legato says.

The result: Guys often take many more risks (which you probably already realize if your small son has taken one too many spins off his bike handlebars). “Almost inevitably, a male will take risks that a woman of his same age wouldn’t take,” Dr. Legato says.

Women succumb to heart disease later

Heart disease is the leading killer of both men and women, but men are more likely to develop it—and die from it—as early as their 30s and 40s. Women, on the other hand, typically develop heart disease 10 years later than men. They’re protected from it until menopause, since their bodies churn out estrogen, which helps keep arteries strong and flexible, says Dr. Legato.

HEALTH.COM: 15 Weird Things Linked to Heart Attacks

Women have stronger social networks

Friends make good medicine: People with strong social connections have a 50% lower chance of dying than those with few social ties, according to a 2010 study at Brigham Young University. “Most men tend to hold their stress and worries close to their chest, while women tend to reach out and talk to others,” Dr. Legato explains. The one exception: married men, which also explains why so many studies show that they’re likely to be healthier and live longer.

HEALTH.COM: How Friends Make You Healthier

Women take better care of their health

Men are 24% less likely than women to have visited a doctor within the past year and are 22% more likely to skip out on cholesterol testing, according to the Agency for Healthcare Research and Quality. In fact more than a quarter (28%) of men don’t have a regular physician and about one in five didn’t have health insurance in 2012, according to the Kaiser Family Foundation.

You can blame it on the so-called John Wayne syndrome: “Men often deny illness; they minimize symptoms because they don’t want to go to a doctor and find out something is wrong,” Dr. Legato notes.

HEALTH.COM: 10 Worst States for Women’s Health

This article originally appeared on Health.com

TIME women

My Hair Will Never Go Gray, and It’s Lame

Gray hair
Getty Images

It’s a “blessing” of genetics, but I’m starting to question how much of a blessing it is

xojane

This story originally appeared on xoJane.com.

I know you’re laughing at the title, because I’ve heard that laugh before. The one that says “You’ll understand when you’re older.”

I heard that laugh a lot the time I grew a single strand of silver, courtesy of an upper management change at my job that made things unbearably stressful.

“This job is literally killing me!” I’d tell my friends. “I have a gray hair! I’M NOT SUPPOSED TO HAVE A GRAY HAIR!”

“Oh, it’ll have friends soon enough!” they said, laughing condescendingly. But I wasn’t upset because it was a sign of age. I was upset because it was a sign of overwhelming stress. My best friend plucked it because I wouldn’t shut up about it. Now I wish he had left it.

I’m about to turn 36, and that’s the only gray hair I’ve ever had. After I escaped from that job, it even grew back brown. My mother, at 56, has never even had one. Her mother didn’t go gray until the illness that took her life in her 70s. (My father’s side, for the record, goes salt-and-pepper in their 20s, so I know I don’t take after him.) It’s a “blessing” of genetics, but I’m starting to question how much of a blessing it is.

It doesn’t help that, regardless of my hair color, I looked 17 at 25 and now look 25 at 35. I live in a big college city and people constantly assume I’m a student. I spent most of my 20s trying to reassure people I was actually legal. I keep my driver’s license handy so I can whip it out as proof that I’m not a kid. A bouncer at a club once was intent on finding the flaw that proved my ID was fake or at the very least belonged to my older sister. A friend who I graduated high school with was, on multiple occasions, mistaken for my father. Another friend joked that he assumed anyone who dated me was a closet pedophile.

People always said I’d appreciate my youthful looks when I was older, but honestly, I’m still not seeing it.

Because looking much younger than you are — not just for a night out partying but every single day — really, really sucks. There’s a respect that comes with age that I don’t receive. I have an untraditional life — I’m a lesbian, I’m taking some single time after spending most of my life in serious relationships with men thanks to self-denial, and I just don’t want to have children. Maybe if I had some gray hairs, people who are even younger than me would stop telling me I’ll change my mind and want to settle down to have a family someday.

No, my sleep-all-day, work-all-night solo lifestyle is the result of conscious decisions based on many years of valid life experience and not just juvenile whim.

And what do I get out of looking young? Being more attractive to younger men? I’m an introverted lesbian with an anxiety disorder. I’d much prefer to be occasionally taken seriously.

I could live with my baby face if I just had some gray hair to offset it. Most people who look younger than they are eventually get that much to balance it out. But not me. I’m “blessed” with a lifetime of not being taken seriously, of having my choices dismissed, of even getting passed up for promotions because of vague claims that I wasn’t respected enough. Nature, throw me a bone here!

I know a lot of people, especially women, hate going gray. But I for one could really go for some of that visible aging right about now.

J. J. Ulm is a fiction writer living in Ohio.

TIME Ideas hosts the world's leading voices, providing commentary and expertise on the most compelling events in news, society, and culture. We welcome outside contributions. To submit a piece, email ideas@time.com.

TIME neuroscience

This Alzheimer’s Breakthrough Could Be a Game Changer

Scientists recreated what goes on in the brains of Alzheimer’s patients in a 3D culture dish that could speed development of new drugs for the disease

Researchers have overcome a major barrier in the study of Alzheimer’s that could pave the way for breakthroughs in our understanding of the disease, a new report shows—and that new understanding could, in turn, pave the way for drugs that treat or interrupt the progression of the neurodegenerative condition.

For decades, animals have been the stand-ins for studying human disease, and for good reason. Their shorter lifespans mean they can model human conditions in weeks or months, and their cells can be useful for testing promising new drug treatments.

But they haven’t been so helpful in studying Alzheimer’s disease. Two factors contribute to the neurodegenerative condition — the buildup of sticky plaques of the protein amyloid, and the toxic web of another protein, tau, which strangles healthy nerve cells and leaves behind a tangled mess of dead and dying neurons. Despite attempts by scientists to engineer mice who exhibit both factors, they haven’t been able to generate the tau tangles that contribute to the disease.

Now, Dr. Rudolph Tanzi and Dr. Doo Kim at the Mass General Institute for Neurodegenerative Diseases at Massachusetts General Hospital, have devised a work-around that doesn’t involve animals. They have developed a way to watch the disease progress in a lab dish.

“In this new system that we call ‘Alzheimer’s-in-a-dish,’ we’ve been able to show for the first time that amyloid deposition is sufficient to lead to tangles and subsequent cell death,” said Tanzi in a statement.

MORE: Blood Test for Alzheimer’s

While autopsies showed evidence of both amyloid and tau in the brain, Alzheimer’s experts have been debating for years which came first — do amyloid plaques trigger the formation of tau tangles, or does the presence of tau cause amyloid to get stickier and bunch together in the brain? Tanzi and his colleagues showed definitively for the first time that amyloid is the first step in the Alzheimer’s process, followed by tau tangles. When he blocked the formation of amyloid in the culture with a known amyloid inhibitor, tau tangles never formed.

The disease-in-a-dish model is an emerging way of understanding conditions that either can’t be recapitulated accurately in animals, or diseases that make it difficult to study and test in human patients. In recent years, for example, scientists have successfully recreated the process behind amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s disease, using stem cells from patients and allowing them to develop into the motor neurons that are affected by the disease. The technique led to a breakthrough in understanding that a certain population of nerve cells known as glial cells poison the motor neurons and impede their normal function. Now experts are focusing on finding ways to control the glial cell activity as possible treatment for ALS.

MORE: How Moodiness and Jealousy May Lead to Alzheimer’s

Tanzi and his team are hoping that something similar will come from their model of Alzheimer’s.

While the genes responsible for the inherited form of Alzheimer’s differ slightly from those involved in the more common form that affects people as they age, the end result — the build up of amyloid plaques and tau tangles — are the same. So now that they can see both the clumps of amyloid and the tau tangles, form, they can start to tease apart the processes that link the two processes together.

That will open the way toward finding drugs or other ways of interrupting the process more quickly than they could working with animals. It took six to eight weeks for the cells in the dish to form plaques and then tangles, compared to a year or so in mice. “We can now screen hundreds of thousands of drugs in this system that recapitulates both plaques and tangles…in a matter of months,” Tanzi said. “This was not possible in mouse models.” The system also makes it possible to test these drug compounds at one-tenth the cost of evaluating them in mice, he said. And that means that finding a way to prevent Alzheimer’s may come both faster and cheaper than scientists had expected.

MONEY Social Security

This Little-Known Social Security Strategy Can Boost Your Retirement Income

woman flicking light switch
JGI/Jamie Grill—Getty Images

For retirees who need added income temporarily, turning your Social Security benefit on and off can be a smart move. It may also help your family over the long term.

Welcome to the Social Security claiming world of start-stop-start, a sophisticated strategy that can add big bucks to some people’s lifetime benefits if properly used.

By now, anyone who regularly reads about Social Security likely knows that delaying benefits until age 70 allows them to reach their highest level.

They also probably know that beginning to collect retirement benefits as early as age 62 will reduce them by 25% from what they would have been at age 66 (and 76% from their level at age 70 if claiming is deferred).

But it’s a whole lot less likely that they know about being able to begin taking benefits early, stopping them at age 66, and enjoying the benefits of delayed retirement credits until age 70. This is a potentially great option that can boost lifetime benefits, as well as help people who may be in a temporary financial bind in their early 60s—perhaps they have to take early retirement, but later end up earning more money in a second career.

Larry Kotlikoff, an economics professor (and co-author of my upcoming book on Social Security claiming), provides a useful and detailed explanation of the start-stop-start strategy. His analysis includes extensive computer simulations to determine how best to take advantage of these rules.

How Start-Stop-Start Works

The flexibility to start and stop your benefit is yet another important aspect of the agency’s rules regarding what it calls Full Retirement Age (FRA). This is 66 for people born between 1943 and 1955. For people born later, it rises by two months a year before hitting 67 for anyone born in 1960 and later. (I wrote recently about how the FRA can affect claiming decisions.)

I recommend that people consider waiting until age 70 to begin Social Security. But there are lots of valid reasons to begin claiming as soon as 62, which normally is the soonest you can receive benefits (there are earlier claiming ages for people with disabilities and surviving spouses).

If you take reduced benefits early—with “early” meaning before your FRA—you generally are stuck at those reduced benefit levels until you reach your FRA. There is a provision that lets you withdraw your benefit decision within a year of making it, pay back everything you’ve received from Social Security (included Medicare premium payments, if applicable) and get a fresh start with your claiming record.

But most early claimers don’t do this. Once they file early, they are stuck with whatever reduced benefit they get until they hit their FRA. At that time, Social Security rules allow a person to suspend their benefits for as long as four years. This is the “stop” part of start-stop-start. And most people are not aware of this FRA-related rule.

During this “stop” period, their benefits will earn delayed retirement credits. If they suspend for the full four years before their second “start,” their benefit will be 32% higher than when they suspended it. That’s a real 32% gain, too, as the delayed credits include the program’s annual cost-of-living adjustments for inflation. Now, this person’s benefits at age 70 will still be less than if they had never claimed a reduced benefit. But they’ll still be much higher than if they had never suspended them at their FRA.

Here’s a simple example: Say you are due a $1,000 retirement benefit at your FRA of 66. It will rise 32% to $1,320 a month (in real, inflation-adjusted terms) if you wait to claim until you turn 70. It will be reduced 25% to $750 a month if you claim early at age 62. However, that $750 will rise by 32% to $990 a month if you suspend at age 66 (the “stop”) and resume (the second “start”) at age 70. That’s a lot more than $750, of course, but it’s still far short of the $1,320 you’d get if you never claimed benefits at all until you turned 70.

Who Benefits by Resetting Your Claim

Besides helping out those in a temporary financial bind, this strategy may also improve your spouse’s benefits. Under Social Security rules, one spouse has to first file for their retirement benefit before the second spouse can file for a spousal benefit. While filing for retirement early will reduce that filer’s benefits, it could increase your family’s overall income. That’s because your husband or wife can then collect spousal benefits, while his or her individual benefit will keep rising till age 70.

If there’s a big age difference between you and your spouse, or if your spouse has a work record to consider, it can make sense for one spouse to begin benefits early, then suspend them when the second spouse reaches an optimal claiming age. The benefits of start-stop-start can become particularly valuable in maximizing family benefits for a couple, especially if they have young children.

As you can see, calculations for how to maximize benefits using start-stop-start can be very complex. You will probably do best to get help from a financial adviser, or use a benefits claiming calculator (see some recommendations here and here), or both.

Philip Moeller is an expert on retirement, aging, and health. He is an award-winning business journalist and a research fellow at the Sloan Center on Aging & Work at Boston College. Reach him at moeller.philip@gmail.com or @PhilMoeller on Twitter.

TIME Aging

Quiz: How Long Will You Live?

baby
Getty Images

8 questions that help determine your life span

Americans can now expect to live longer than ever, a new government report finds. That’s largely because death rates are declining for the leading causes of death, like heart disease, cancer and stroke.

How long will you live? These eight basic questions, calculated by two researchers from the University of Pennsylvania, are some of the most predictive of American life expectancy. “Those are the most important risk factors that we have solid evidence for,” Lyle Ungar, professor of computer and information science at the University of Pennsylvania, tells TIME.

The one missing factor? “If you’re in a happy marriage, you will tend to live longer,” he says. “That’s perhaps as important as not smoking, which is to say: huge.” So feel free to give yourself a little bump if you’ve got a happy relationship.

Find out yours in the quiz below (and if you’re on your phone, turn your device sideways):

via Life Expectancy Calculator from Lyle Ungar and Dean Foster

Read next: Eat More Mediterranean Foods Now: Your Later Self Will Thank You

TIME Aging

Men’s Bone Health Is Largely Ignored

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Why men need to start saving their skeletons

A third of all hip fractures happen in men, and in the year after a fracture, men are twice as likely to die as women. That’s due, in part, to the fact that men don’t get treated as often as women do for osteoporosis, a new report from the International Osteoporosis Foundation says.

In fact, men’s bone health is largely ignored, and one study showed that men are half as likely as women to get treatment. About 20% of men over 50 have osteoporosis fractures, a number set to rise with the aging population, the report says. From 2010-2030, the number of hip fractures in American men is set to rise 52%, while the number among women is expected to drop by nearly 4% (likely because women are routinely screened for bone loss and are treated preventively).

The lifetime risk of a bone fracture for men is now higher than the risk for getting prostate cancer, and those who smoke, drink heavily, or have vitamin D, testosterone or calcium deficiencies are especially at risk. “People should not have to live with the pain and suffering caused by osteoporosis as we can help prevent and control the disease,” says Professor John A. Kanis, president of the International Osteoporosis Foundation, in a statement.

One of the best lifestyles switches men can make for their bones is to exercise more. Men lose muscle as they age, which makes bones much more vulnerable. Weight-bearing exercise protects against bone loss and falls, and these 6 best anti-aging exercises for men are proven to make aging men stronger.

MONEY

Here’s the Only State Where Retirees Have Enough Income

Just one state plus the District of Columbia have typical retirees with more than 70% of pre-retirement income. Traditional pensions and low cost of living make a difference.

The problems retirees encounter trying to secure lifetime income know no bounds: In 49 states those past the age of 65, on average, fall short of a widely accepted benchmark for minimum income in retirement, new research shows.

Financial advisers generally agree you need at least 70% of pre-retirement income to maintain your lifestyle after calling it quits. Many say 80% to 85% is a more appropriate target.

But even using the lower bar, Nevada is the only state where the typical retiree has sufficient income to live comfortably in retirement, according to a study from Interest.com, a division of Bankrate, a financial information provider. The District of Columbia also makes the cut. But every other jurisdiction in the nation falls short, underscoring the scope of the retirement income crisis in America.

Nationally, the median income for those who are 65 and older equals just 60% of the median income for those aged 45 to 64, the study found. In Nevada, median income for those past 65 is 71%. In Washington D.C., the figure is 74%. States that get close to the minimum retirement income level are Hawaii (69%), Arizona (68%) and Mississippi (68%). At the bottom are Massachusetts (49%) and North Dakota (49%).

The national rate represents a jump of 10 percentage points over the past decade. But that is not as encouraging as it may appear, reflecting trends where older Americans stay on the job longer and young workers fail to see significant wage gains. The share of Americans working past 65 has been increasing for 20 years and reached 18.9% this May, one of the highest levels in the last half century.

Washington D.C. tops the retirement income list in large measure because of its huge population of retired federal employees, many of who have generous traditional pension plans. Nevada (along with Arizona and Mississippi) benefits from a low cost of living; the costs of food, housing, utilities, transportation and medical care in Reno, Nev., are just 67% of such costs in Washington D.C.

Hawaii is one of the most expensive places on Earth to retire. But it measures up well in this study because the state has a strong traditional pension culture. It may also help that wealthy people choose it as their retirement destination. At the bottom, Massachusetts (like much of the Northeast) has long suffered from a high cost of living while North Dakota recently has seen its cost of living soar amid an oil boom in that state.

MONEY retirement age

How to Know When It’s Time to Retire

Birthday candles
Fuse—Getty Images

I’ve long argued that one’s quality of life should be a principal factor in deciding when to retire. At the same time, however, financial considerations can’t be ignored. With this in mind, here are three rules of thumb to help you decide whether you’ve reached the perfect age to retire.

1. Have you saved enough money?

The “multiply by-25″ rule is a popular tool that retirement experts encourage people to use to estimate whether they’ve saved enough money to stop working and, at least hopefully, begin a life of leisure.

Here’s how it works: Multiply your desired annual income in retirement, less projected annual Social Security benefits, by 25. If your savings are greater than that, then you’re in good shape. If not, then you may not be financially ready to retire.

For example, let’s say that Bob and Mary Jane estimate they’ll spend $40,000 a year in retirement. Using the rule of 25, they’ll need savings of $1 million.

A slightly different iteration of this is the “multiply by-300″ rule. This is the same thing, but it focuses on months instead of years — that is, take your average monthly expenditures, minus your monthly Social Security check, and multiply that by 300.

If your savings are greater than that, then you’re all set. If not, then you might want to continue working for a few more years.

2. Will you have enough income?

This question is related to the first one, but it attacks the issue from a slightly different angle. As such, it also has its own rule of thumb: the 4% rule.

This rule holds that you can safely withdraw 4% from your portfolio every year and still be confident it will last through retirement. Thus, to determine if you’ll have enough income in retirement, multiply your portfolio by 4% and then add in your projected annual Social Security benefits — to learn one potential problem with this rule, click here.

If the sum of these two numbers is enough to cover your expenses, then you’re ready to retire. If not, then it may behoove you to put off retirement for a while longer, as doing so should allow your portfolio to continue growing. It will also give your Social Security benefits time to accrue delayed retirement credits.

3. Is your portfolio properly allocated?

Finally, determining if you’re ready to retire isn’t just about how much you’ve saved, it’s also about how your savings are allocated into various asset classes — namely, stocks and bonds.

To be ready for retirement, you want to make sure that your assets are invested in as safe of a way as possible. To do so, it’s smart to steer your portfolio increasingly toward fixed-income investments like bonds as you approach your desired retirement age.

Experts use the following rule to determine the proper allocation: “The percentage of your portfolio invested in bonds should equal your age.” Thus, if you’re 60 years old, then 60% of your portfolio should be in bonds and 40% in stocks. If you’re 55, then the split is 55% to 45%, respectively.

While this may seem like it has less to do with the timing of retirement than the former two rules, the reality is that it’s of equal importance. As my colleague Morgan Housel has discussed in the past, one of investors’ biggest mistakes is to underestimate the volatility in the stock market. According to Morgan’s research, stocks fall by an average of 10% once every 11 months.

Suffice it to say, a drop of this magnitude would have a material impact on both of the preceding rules, as a 10% decline in your stock holdings would equate to a much smaller income under the 4% rule and, as a corollary, it would call for a delayed retirement date under the multiply by-25 rule.

And the impact of this would be even more exaggerated if the lions’ share of your assets were still in stocks as opposed to bonds. Consequently, the culmination of your strategy to bring your portfolio into accord with this final rule is a key step in determining the perfect age at which you’re ready to pull the trigger and actually retire.

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