SAN FRANCISCO (Business 2.0 Magazine) -- We've reached the balmy days of August, but for a growing number of workers chained to their jobs, it might as well be January.

U.S. employees are taking less time off than ever: Not only is the average number of annual vacation days granted to them a mere 12.4 - less than that of the average medieval peasant - but more than a third of us don't even use all of our allotted time off.

Collectively, American workers give a whopping 1.6 million years' worth of unused vacation time back to their employers every year. We may like to think of ourselves as charitable, but this is ridiculous.

Even worse, at least 20 percent of us admit to sneaking some work along with us during our paltry vacation time, according to the New York-based Families and Work Institute. The American Management Institute puts the figure at closer to 50 percent. Either way, the trend appears to be increasing. An Intel (Charts) survey last month found that 53 percent of us would like to take laptops on future vacations, mostly so we can sneak a peak at our work email.

Whether you're reading this in a sun-free cubicle or in a crowded Internet café at some tropical resort, you may well be wondering what happened to the leisure economy we were promised would kick in by the 21st century.

The answer is that it's here; we just haven't figured out how to take advantage of it yet. But there are a few glimmers of hope on the horizon. Here are four reasons why working smarter rather than harder will soon be more than a glib slogan.

1. Economics. Employers are starting to understand that stress is killing their workforce and driving up health costs. The Framingham Heart Study, conducted over 20 years, found that women who took two or more vacations a year cut their risk of a fatal heart attack in half, and a 2000 study reached similar conclusions for men.

Yet more studies have shown, not surprisingly, that an overworked employee is more likely to make mistakes and get angry at their bosses - and 30 percent of us feel chronically overworked. Indeed, job burnout costs the U.S. economy an estimated $300 billion a year in accidents, employee turnover, diminished productivity and medical costs, according to the American Institute of Stress.

2. Globalization. It is getting increasingly hard to ignore the fact that the Land of the Free is by no means the Land of Free Time. Americans work more days than anyone else in the industrialized world. We all know how relatively lackadaisical Europeans are - the French get seven and a half weeks of vacation a year on average, Italians take eight and a half, and even the efficient Germans manage to squeeze seven weeks of nothing into every year.

But did you know that Japan, where pride in overworking runs deep in the culture, gives workers an average of five weeks off? Or that this very week in the busy hive of South Korea, 51 percent of all families are on vacation, according to the Korea Transport Institute?

It will soon come down to the competition for talent. The more mobile and international business becomes, the more American firms are going to find themselves competing for the finest minds with foreign companies that offer very attractive vacation packages.

If you're a stressed-out executive with a heart condition and a family you never see, an extra few thousand dollars in a year's worth of paychecks may not amount to much. But an extra five weeks every summer with the kids in an Italian villa? Priceless.

3. Demographics. In an essay entitled "Cube Dwellers Flex Their Muscle" last October, Business 2.0 contributor Eric Hellweg wrote that there's a demographic storm coming to the American workplace. Baby boomers are about to start retiring in vast quantities, and the pool of skilled workers at home is shrinking. By 2008, there will be six million vacant jobs requiring some technical background. Companies are either going to have to fill them with H1-B immigrants, who are used to more vacation time, or poach people from rivals with more attractive packages (read: more time off).

At the same time, unions like the Service Employees International Union have started massive recruitment drives for white-collar workers. The more organized cube-dwellers get, the likelier it is that they'll start pushing for - at the very least - the same vacation time their parents got.

4. Tourism. Whether Americans are currently taking advantage of it or not, the tourism industry is one of the fastest-growing sectors in the world. Timesharing, a concept that pretty much locks you in to a minimum amount of vacation time every year, continues to increase in popularity. And medical tourism is expected to be a $40 billion business by 2010, mostly fueled by Americans fleeing pricey health care at home. Not only will you need to take more than a few weeks to recover from your hip surgery in Mumbai, you'll also want some extra time to see the sights while you're there.

Then there's the kind of luxury 21st-century tourism we're only just beginning to imagine: sub-orbital jaunts on SpaceShipTwo, for example, or the four-level, 200-unit floating condominiums being planned by a St. Paul, Minn. developer, whose residents will cruise up and down the Mississippi without ever leaving home.

Given the increasing range of leisure opportunities, it would be surprising if more of us didn't want to take advantage of them - perhaps even permanently, thanks to the rising tide of telecommuting.

In the future you may still be answering work emails from an Internet café in the tropics, but for 52 weeks a year rather than just one.