Once upon a time in a land close at hand, a Great Wizard came to the people with a special gift: an extra 10 years of good health! A bonus of time and vitality for the whole population! The period called youth would now last until about age 60!

At first, the people were pleased. Politicians took credit, citing funds for medical research and high-tech healthcare. Scientists raced to study the impact of this wondrous gift on people's lives.

At Stanford University, economics professor John B. Shoven put a different lens on his demographic telescope to explore the Big Shift that has occurred in aging. He argues that age should be calculated not by years since birth but by years left to live. With data from the 2000 census, he has reconfigured the calendar of aging, creating a long period of youth followed by shorter periods of middle age and old age.

Forget your date of birth! Your chance of dying within a year tells you your real age. "You're young if you have lower than a 1 percent risk of dying within the year," Shoven explains. "Women are 63 before they get to that point."

Sixty and young? He's not saying that 60 is the new 30. (It's not; I've been both.) But according to his mortality risk measure, you aren't old unless you have a 4 percent risk, Shoven says. That's a 1-in-25 chance of dying within the year, which could well translate into a lengthy old age. Today, people don't begin to get old until their 70s. Middle age — defined by a mortality risk between 1 percent and 4 percent — doesn't start for a man until he is 58!

Just like dollars, years of age don't have the same value as they did in the past. In 1940, a man in his late 40s had the same mortality risk as a man in his late 50s today. A woman in 1940 crossed the threshold into old age when she was in her late 60s. Today she would be in her late 70s.

The Extra Ten! Shoven's mortality risk measure shows how the Wizard's gift has reshaped the population, overturning traditional concepts of growing old and creating vast numbers of men and women who should now be considered young.

Look at House Speaker Nancy Pelosi, 67, the icon of Granny Glam. Look at the presidential candidates, a group of oldies, according to their birthdays. But not by the new age measure: Hillary Clinton, nearly 60, is a spring chicken. John McCain, 71, merely middle-aged! And just last week, the Centers for Disease Control and Prevention released data on life expectancy in the United States: A child born in 2005 can expect to live for almost 78 years, an increase of about two years over children born a decade earlier.

"It's all good news," Shoven says. "The end is still bad, but it's being pushed out further." The Extra Ten "are good years."

But the people grew wary of the Wizard's gift. They turned against aging. A vast anti-aging industry sprung up offering a range of products from supplements to turn-back-the-clock surgery. No one wanted to grow old. They worried about their future, what they would do in the Extra Ten, how they would support themselves, who would be there for them when they got sick. They began to lose sight of their gift.

Meanwhile, the politicians had fled the scene. For them, the gift was trouble. They feared a tsunami of old folks washing over the land, bankrupting the Treasury, overwhelming healthcare.

Meanwhile, Stanford's Shoven is trying to calm the populace. The dramatic increase in people older than 65 will not be a catastrophe because they will not be like 65-year-olds of yore. If the Extra Ten is a gift that keeps on giving, only 14.8 percent of the population will have a mortality risk of 1.5 percent or higher — a relatively modest increase compared with today.