What would you do with an extra $806? Invest it? Pay down debt? Take a long weekend trip? If you're like the average working American, you'd give it to your employer and get nothing in return. That's in effect what happened last year because so many Americans chose to lose rather than use their paid time off, according to the US Travel Association, a trade group whose Travel Effect project is designed to encourage Americans to take their vacation days. 

You wouldn't think it would be hard to get people to chill out, but apparently it is. According to an analysis of Bureau of Labor Statistics data by Oxford Economics and GfK Public Affairs for USTA, workers in this country lost a total of 169 million days of earned PTO (defined as vacation and personal days) last year. Those days were not rolled over to the next calendar year or cashed in. They're just gone, stricken from the books, because workers elected not to use them. 

Travel Effect's latest video drives home the lost-pay point. 

Not taking vacation days is like throwing away money
There's a vast disconnect between the stereotype of the hardworking American hustling to earn more coin and the reality that Americans permanently gave up such a huge number of vacation days in 2013 -- an average of 1.6 days per employee. The study assumed an average dollar value of $504 per forfeited vacation day per American, or a collective $52 billion dollars -- $806 per employee -- that American workers said "no thanks" to in 2013. 

It's true that most employers don't allow current employees to cash in unused days. That's often reserved for settling up when an employee moves on to a new company. But most of us would consider a day off better than working for nothing. 

Americans leave nearly 5 vacation days on the table each year
It turns out the lost day and a half is just the tip of the unused-PTO iceberg. The Travel Effect study, which was sponsored by American Express, found that 4.9 of the 21 PTO days the typical American earns go unused each year. Less than half of the workers who skip vacations can roll over their time to the next year, and a quarter of them lose those days permanently at year's end -- meaning that even if they leave the company in the future, they'll never reap the cash value of those expired days. 

Holding back a few vacation days in case of emergencies might make sense, but letting those days expire is a waste. Cait Douglas, Travel Effect communications director, would like workers to be more aware of what their time off is worth. "You would hope by Americans having this number, they will start to rethink the value, beyond just the dollar terms, of the time they're leaving behind," Douglas said in an email conversation with The Motley Fool. 

There's no correlation between skipping vacations and performing better
Workers must be getting something out of this sacrifice on their part, or at least think they are. But more time at the office doesn't correlate with more money in the paycheck. In fact, the reverse may be true. Workers who left 11 to 15 PTO days unused last year might look more valuable than the folks who took all their vacation days, but Oxford found they were 6.5% less likely to have earned a bonus or a pay raise in the last three years.

Correlation isn't causation, and it's possible that workers who've been passed over for a raise may feel the need to double down and skip vacations to prove their worth to their employers. But the lack of break time could be damaging their effectiveness on the job. Oxford found a "clear correlation" between leaving more than 11 days of PTO unused and reporting high levels of stress at work. 

The takeaway: use your time off
What's the solution? Obviously, the Travel Effect campaign is geared toward getting people to take their time off and go on vacations. The report figured that if Americans took vacation days now at the rate they did before 2000, it would add $284 billion to the overall economy, including nontravel spending. But even if workers can't afford to take a "real" vacation, a day off spent doing nothing every now and then is pretty close to priceless -- especially since it's already paid for.

Casey Kelly-Barton has no position in any stocks mentioned. The Motley Fool recommends American Express. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.