American workers are definitely time wasters — they wastemillions of hours of paid time off every year because they're toobusy working to use the PTO they've accumulated.

In its second survey in four months, the U.S. Travel Associationattempted to quantify the “cost” to employees of not taking theirPTO. An earlier survey revealed the reasonsbehind the tendency not to use all of one's PTO.

This time around, here are the numbers that emerged from thedata-crunching:

• American workers permanently lost a total of 169 million daysof paid time off across the workforce in2013;
• American employees give up $52.4 billion in benefits by nottaking their full PTO;
• The average cost per employee is $504;
• U.S. employees took an average of 16 vacation days in 2013compared to an average of 20.3 days as recently as 2000.
• U.S. employees who left 11-15 days unused are less likely(by 6.5 percent) to receive a raise or bonus than those who usedall of their vacation days;

Those who leave 11 days or more unused reported being “very” or“extremely” stressed with their work lives, compared to those wholeft less time on the table or took all their PTO (31 percent vs.25 percent).