One more time…438 million.

That’s the estimated number of vacation days Americans failed to take in 2007.

This is from Howard Shapiro of The Philadelphia Inquirer, “Taking time off? A lot of Americans prefer to work.”

Here are a few of the highlights:

“I think it’s an epidemic. We take less of the pitiful amount of vacation time we have than anybody else on the planet. We are genuine to-the-bone workaholics, and even if it’s killing us, we’re still doing it.”

Not only do we regularly give up days we’ve often bargained hard to get, we also get few compared with the rest of the industrialized world. In fact, the United States is singular when it comes to vacation days: We are the only advanced economy in the world without a minute of government-mandated time off.

In order to be a member of the European Union, a nation’s employers must offer workers a minimum of 20 days off a year. Several mandate more. According to “No-Vacation Nation,” a study by the Center for Economic and Policy Research about the United States’ unique place in the balance between work and lifestyle, France requires the most vacation: 30 days, plus a paid holiday. Overall, though, the French are beaten by Austria and Portugal, which require employers to give 22 vacation days off, plus 13 holidays, for a total of 35 days off — amounting to seven weeks a year.

Among the richest countries, Canada and Japan mandate the fewest days off, not counting the U.S. total of zero. The Japanese, who have a word — karoshi — for dying from overwork, get a minimum of 10 days and no nationally mandated holidays. Canadians have the same minimum, but get an additional eight paid holidays.

Workaholism. The Puritan ethic. Feeling guilty about taking earned days. The fear of being overrun by competition. People frequently cite these reasons for junking their vacation days.

Go ahead…take a holiday.