Source: http://www.msn.com/en-us/money/careerand...

U.S. workers are using only 77 percent of their paid time off, according to the research group's report released Tuesday. And the decline is not just tied to recent economic worries; use of vacation days are at their lowest point in the past four decades. In 2013, U.S. workers took an average of 16 days of vacation compared with 20.3 days in 2000, according to the report.

The study, commissioned by the U.S. Travel Association, found that American workers earned just under 21 paid-time-off days in 2013 (excluding sick days,) but used only 16. And while some employees are allowed to bank or roll over their vacation days into the next year, an average of 1.6 days were completely forfeited, according to the survey.

In total, that's about 169 million days forfeited, amounting to $52.4 billion in lost benefits.

Other studies have highlighted the other cost of all those unused vacation days to employees—and companies. According to internal research by audit firm EY (formerly Ernst & Young), employees who use more vacation days end up with better performance reviews. Taking vacations can also help slow down employee turnover, saving companies the cost and effort of recruiting and training new hires. Other research has linked vacation time to increased worker productivity.