Paid vacation is a nice perk of any job – but not all Americans are taking advantage of their days off. A new survey finds that more than half of Americans will not use all the vacation days they are allowed.

The survey, conducted by Bankrate, found that 52 percent of American employees who receive some sort of paid time off will not take all those days — compared with 47 percent who say they will use every last hour.

According to the survey, 64 percent of Americans receive some sort of vacation time.

Of those 52 percent who are leaving time on the table, most say they will not use at least one of their allotted days.

Gen-Xers use the least of their vacation time, with 53 percent not taking all time allotted. That is followed by 44 percent of Millennials and 43 percent of Baby Boomers.

One-quarter of young millennials – between the ages of 18 an 25 – said they’re not using any of their vacation time.

Respondents cited numerous reasons for not using all their vacation time, including saving up days – and just having too much work to do.