There’s no question that vacation time matters. I speak constantly about the importance of taking time off, noting that people who take vacations regularly report being happier. I also experience this phenomenon first-hand—I’ve got a super-busy job here at Expedia, but I know that when I take vacation with my husband and my kids, I feel better physically and mentally, and feel more connected to them all.

The problem: As Americans, we aren’t taking nearly as much vacation as we should—or, it turns out, as much vacation as we COULD. This is the gist of the findings from our 2015 Vacation Deprivation study, our fifteenth annual look at how people with full-time jobs in a variety of countries around the world treat time off. (For a look at the 2014 data, click here.)

This year’s study, conducted on behalf of Expedia by Northstar, a strategic insights consulting firm, culled responses from 9,273 employed adults across 26 countries in Asia Pacific, Europe, North America, and South America.

There’s a ton of data in the 2015 study—check out the formal press release here.

Because I’m a U.S. citizen, because Expedia is headquartered in the United States, the most recent study results that resonate strongest with me pertain to America.

American workers report leaving four full days of vacation on the table each year, with 15 available and 11 taken. Do the math and you’ll see this amounts to just less than 500 million unused vacation days a year in the United States.

(As an aside, the U.S. Travel Association has studied the issue of vacation use as well, and has published and promoted many of its findings through an effort called Project: Time Off. It’s an effort we support.)

Some other high-level points from the 2015 Expedia Vacation Deprivation study:

  • Worldwide, according to respondents, the median number of paid vacation days available to workers is just under 25 days per year, in addition to holidays.
  • Collectively, responding workers take about 20 of these days, leaving five, or 20 percent, unused.
  • Globally, 19 percent of respondents reported a desire to “bank” vacation days for the next year as a possible reason for not using all of their vacation days.
  • Roughly 51 percent of respondents typically take vacations in smaller, more regular chunks: several short vacations and long weekends. About 32 percent take one long holiday.

Best and worst

One of the most notable attributes of data from our 2015 Vacation Deprivation study is how far-reaching it is. We don’t only collect information about vacation time in our home country, but also about vacation time in countries all over the world.

This gives us some fascinating context about which nations are the best at taking time off, and which are, well, the worst.

More numbers for you:

  • Europeans and Brazilians are the world’s least-deprived vacationers—people from these nations get and take the most vacation time of all.
  • South Koreans are the world’s most vacation-deprived workers; people from this country are offered 15 days on average but take only six.
  • Workers from the UAE receive and take almost twice as many vacation days as their peers across APAC.

In a statistic I find surprising, only 15 percent of workers worldwide say they would leave their current jobs for one that offers more vacation time, and that 69 percent of workers would choose “a pay raise” over “more vacation days.” Sure, money talks, but vacation is important, too!

I also couldn’t believe the numbers what study respondents actually do on vacation. About 25 percent of respondents claimed to check their work email and phone messages once per day while on vacation, while about 22 percent of respondents said they feel “somewhat guilty” for taking their vacation time in the first place.

Thankfully, our research on the impact of vacation painted a different picture. A whopping 85 percent of respondents said they “somewhat or strongly agree” that they feel happier after a vacation, and 92 percent of American respondents agreed with this statement. This tells me I’m not alone in feeling rejuvenated after time away from work. If only we could get the rest of the world to feel the same, we full-time workers would be a much happier bunch.