Fifty-five percent of employees don’t use all of their vacation days, according to Project: Time Off. (iStock)

Cue “Holiday Road” and break out the car polish for the old Family Truckster, because it’s time to plan your next vacation. Tuesday, Jan. 31, is the inaugural National Plan for Vacation Day, an initiative launched by an organization called Project: Time Off to encourage Americans to block off dates and commit to using their vacation time this year.

Apparently, we need all the help we can get. According to Project: Time Off, which is financially supported by the U.S. Travel Association, 55 percent of employees don’t use all of their vacation days.

“Vacation seems to be a casualty of how busy we are,” says Katie Denis, senior program director with Project: Time Off. “Everyone’s busy. The calendar fills up really fast. Take a moment at the beginning of the year to block that calendar so it doesn’t get away from you.”

According to a report, “The State of Vacation in America”, released by Project: Time Off, workers skipped out on 658 million vacation days in 2015, and 222 million of those were lost entirely because they couldn’t be rolled over. That, says Denis, is akin to volunteering for your employer.

“If you volunteer, you should get a free T-shirt and help the planet or something,” says Denis. “You don’t want to volunteer at work.”

Denis says the decline in using vacation time began around 2000. Between 1976 and 2000, Americans used an average of 20.3 vacation days. That number has since declined, and in 2015 it hit 16.2 days.

Researchers looked at all the trends that might be driving the downward shift, and they found that technology made a huge impact: As Internet adoption goes up, vacation usage goes down. Even in this increasingly wireless world, we have become tethered to our desks.

“We’ve always had a strong work ethic as a country. But somewhere along the line, that’s kind of transformed into a work martyrdom,” says Denis. “And that’s what we’re trying to work against, because that’s what drives unhappiness, discontent, and at some point employees leave.”

Employees shared several reasons for why they didn’t take vacation: fears that they would return to a mountain of work (37 percent), no one else can do the job (30 percent), they can’t afford it (30 percent), taking time off is harder as you grow in the company (28 percent), they want to show complete dedication (22 percent), or they don’t want to be seen as replaceable (19 percent).

And yet, vacations can benefit both the employee and the employer. According to Project: Time Off research, two-thirds of employees found that their concentration and productivity improved at work following time off. Senior business leaders agreed, with 91 percent saying that employees returned to work recharged and renewed.

So when Tuesday rolls around, Denis encourages workers across the country to take a look at their calendars, pick some dates for their vacation, request that time off from their boss and start figuring it out. By planning ahead, she says, you’re more likely to follow through with taking time off.

“People who work hard need to take breaks, or they can’t keep doing it,” she says. “We always hear, ‘Oh, it’s a marathon.’ I don’t think work is a marathon anymore. I think work is a series of sprints. And you can’t keep up if you don’t take a moment to rest.”

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