Americans are starting to take more vacation

As the number of job openings reaches record highs, the amount of time Americans spend away from their job is also rising.

Among full-time workers whose employers offer paid time off, the amount of vacation taken has risen for the third straight year. The average time a worker takes per year is now 17.2 days, or just over three working weeks, according to a study from Project: Time Off, a creation of the U.S. Travel Association.

"I think there's a little more confidence among employees now than a few years ago," said Katie Denis, lead researcher on the project. "Employers are giving more time, since they're much more cognizant they have to compete for top talent."  

The uptick reverses a long decline in vacation time that started in the 1990s, according to the analysis. Between the 1970s and 1990s, the average worker took over 20 days off -- even during recessions. Then, in the early 2000s, the averages started dropping. "We lost almost a week between 2000 and 2014," said Denis. The average dropped to 16 days in 2014 before reversing.  

There's still a long way to go, the study found: The average time workers earned (as opposed to average time they took off) was 23 days. That means workers are leaving more than a week of paid time off on the table. This is vacation that's part of their pay package, which means by not taking it, workers are effectively doing their jobs for free, as the Harvard Business Review described it.

And Americans still work many more hours than residents of other industrialized countries. We work nearly two more weeks every year than our counterparts in Japan and nearly three more weeks than the average worker in Australia, according to OECD data.

Mexico takes the prize for the most work, with 2,255 hours per year -- the equivalent of working a 43-hour week for 52 weeks straight.