The end is near. The end of summer, that is. If you're not already planning on taking a vacation soon, it might be time think about getting one on the books.

There are all the usual reasons -- to recharge, to return to work with a fresh perspective and because if your employer provides paid time off, you shouldn't let them go to waste. But now there's one more reason to put in that PTO request. Taking a vacation could increase your chances of getting a raise.

A recent study from the U.S. Travel Association and Project: Time Off explored the state of American vacation. It provides a comprehensive look at our country's vacation-taking habits and how we take (or don't take) vacation affects our happiness, productivity, stress, well-being and even earning potential.

The study surveyed 5,641 American workers who work at least 35 hours per week. They were asked questions pertaining to their own vacation-taking habits and how this impacted their owns lives and the success of their employers.

Over half said they didn't take all of their vacation days last year. Those that did, though, were rewarded financially at work. Employees who took 10 days or fewer of vacation time were less likely to have received a raise or bonus in the last three years than those who took 11 days or more.

Happier employees make for more productive ones

Shawn Achor is the author of The Happiness Advantage and his TED talk about happiness at work has been viewed 13 million times. He recently published a piece with UPenn positive psychology researcher Michelle Gielan in Harvard Business Review. In it, Achor and Gielan explored several reasons why Americans should be taking more vacations. They have long been bringing research to the table that debunks the myth that you should work more to get ahead.

"Our hypothesis has been that without recovery periods, our ability to continue performing at high levels diminishes significantly," the authors wrote. "Statistically, taking more vacation results in greater success at work as well as lower stress and more happiness at work and home."

But, Achor says, you need to do vacation right. If your vacation causes stress -- and many of them do -- then you'll fail to reap the positive benefits of increased happiness productivity at work and home. He recommends you start planning at least a month in advance to look down details such as flights, transportation and lodging. And if you can afford it, go far far away. Those who travel out-of-the country define their trips as more meaningful, Achor says.