CNN Money recently reported that Americans left $67 billion worth of earned but unused vacation days in just 2010. The average American worker used only 14 of their 18 available vacation days. Meanwhile, French citizens used 35 of their 37 vacation days, and workers in Great Britain used 25 of their 28 paid days off.

With 448 million wasted vacation days left on the table in the U.S., employees cite different reasons for staying at the office, including unsupportive bosses or even not being able to trust responsibilities with someone else. Only 38% said they used all of their time-off.

Did you use your vacation time last year? What do you think makes Americans less prone to use their earned vacation days?