Many employees seem to want to reserve vacation time, saving it for the next year, if they are able to roll over time from year to year.

Are you taking some paid time off around the holidays this year? We know a lot of U.S. workers have a hard time disconnecting from work while on vacation. That assumes they’re at least leaving the office—but a new study by online travel company Expedia found that many people aren’t taking full advantage of their vacation time.

According to the “2013 Vacation Deprivation” study, more than 500 million paid vacation days will go unused this year. That number breaks down to about four days per average American worker.

The results are similar to those from a recent survey of HR professionals by the Society for Human Resource Management, which found 61 percent of organizations report that employees, on average, have about three unused vacation days per year.

“We found that features of employers’ vacation plans and the ability to roll over time off determined whether employees took all their vacation time,” Evren Esen, manager of SHRM’s Survey Research Center, said in a statement. “Many employees seem to want to reserve vacation time, saving it for the next year, if they are able to roll over time from year to year.”

Conducted in collaboration with the U.S. Travel Association, the “Vacation’s Impact on the Workplace” survey also found that about a third of companies require their employees to use or lose their vacation days every year, while a little less than two-thirds allow employees to roll them over.

Taking a vacation can affect employee morale, wellness, performance, retention, productivity, and office culture, according to the SHRM study.

More than two-thirds of the surveyed HR professionals said they believe that if employees took more vacation, they would have higher job satisfaction, perform job duties better, increase productivity, and be more engaged at work.

“It is important for managers and company leaders to see the value in employees taking a vacation,” said Lisa Orndorff, SHRM’s manager of employee relations and engagement. “They should also encourage their people to use their leave, ‘unplug’ if possible, and take a break from the work, even if it’s just a day or two every few months.”

How many vacation days will you let go unused this year? Let us know in the comments.

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