The reasons are many. Workers say their businesses don't have enough staff, and they are under too much job pressure to take a long vacation.
The "All Work & No Play" study, commissioned by the Florida's Universal Orlando Resort, found U.S. workers forfeit the equivalent of more than 3 million years of unused vacation time to employers a year.
"Can you imagine your reaction if you were told in a job interview that you were expected to work eight days each year for free?" said Tom Williams, chairman and CEO of Universal Parks and Resorts. "Yet that's what about half of the American workforce is doing."
Employees on the East Coast, the Mid-Atlantic region, New England and Gulf Coast were most likely to forgo earned vacation because of the sluggish economy. Workers on the West Coast and in the Midwest were most likely to use all vacation days.
The survey found employees required to schedule all of their vacation at the beginning of the year were more likely to take all vacation and personal days.