According to one company who allows employees to “buy” and “sell” up to four vacation days a year, only 14% of U.S. businesses offer this unusual benefit. The program, called the Time Off Program, puts employees in charge of managing their traditional vacation time, floating holidays and sick leaves by allowing them to “buy” additional days off without pay or “sell” unused vacation days for pay. The program emerged from a survey conducted by the company to assess work/ life benefits and requests by employees to increase work flexibility.
See "Unusual benefit allows trade of time for money", Carol Kleiman, Chicago Tribune, July 30, 2001