A study by research and polling group Harris Interactive reveals that Americans failed to use about 438 million accumulated vacation days in 2007. Experts list several reasons for workers not using vacation time, including work ethic, stashing accrued time away for a rainy day, and not wanting to be seen as slackers. Harris puts the value of unused vacation time at roughly $60 billion. The United States is the only advanced economy in the world without government-mandated vacation time.
See "Americans lose 438 million days off", Howard Shapiro, The Philadelphia Inquirer, February 18, 2008