Americans average just 10 days off a year, while in Europe, workers are guaranteed 20 days or more of paid leave, plus a generous number of public holidays. And Sir Richard Branson isn't shy about sharing what he thinks about this situation.

"The amount of holiday that people get when they work for American companies, I think, is something of a disgrace," he told a conference recently. "How are you going to find any real time with your children or your partner, real quality time if you have, really, no holiday time?" the Virgin founder wondered.

As vacation-starved Americans know, that's a very valid question. But family bonding isn't  the only reason Americans and their employers should think about moving more toward a European model of more paid leave. Science shows vacations are also good for the careers of individuals and the productivity of companies.

Taking more vacation is good for your career.  

Even among Americans lucky enough to be able to afford lengthier holidays, many worry that taking too much time off will flag them as less dedicated to their work, harming their careers. That's generally silly, according to science. Taking more vacation actually leads to less burnout, greater advancement, and higher salaries.

"A small 2003 study took two groups of employees in the same company, one that took vacation and one that didn't. After coming back from vacation, the vacationers had the same level of stress as the non-vacationers, but much less burnout," Drake Baer reported on the Science of Us blog.

That reduced burnout apparently leads to greater achievement. Another study of more than 5,000 Americans "found that people who took less than 10 vacation days a year had a 34.6 percent chance of getting a raise or bonus in a three-year period, while people who took more than 10 days had a 65.4 percent chance of landing a raise or bonus," Baer continues.

And it's good for your company.

Worries about the career impact of taking more time aren't the only thing holding Americans back from longer vacations, of course. Quite a few of us work for companies that don't give us much -- or any -- paid time off. These firms might think their skimpy leave policies are boosting productivity, but, once again, they should check the research.

The first clue that more time away might be good for output comes from economic statistics on productivity -- vacation-happy Europeans actually produce more per hour than workaholic Americans. Maybe that's because they're not incredibly burned out.  

Research confirms this connection between well rested workers and greater productivity. Here's the conclusion from one study written up recently for "Employees in countries that take more vacation do have a strong desire to get a lot done as well as a tendency to move faster ... [More vacation time] results in greater productivity at work." 

Meanwhile, Stanford's Emma Seppälä points out that "after a vacation, 64 percent of people say that they are 'refreshed and excited to get back to my job,'" adding "another professional advantage from taking time off is a boost in creativity," particularly if your break is completely unplugged and/or involves time in nature.

Is unlimited vacation vacation the answer?

At the conference, Branson went on to tout his companies' unlimited vacation policy, as well as to offer tips on how to convince your boss to adopt one. But these programs can backfire as employees, uncertain and guilt-ridden about how much time is too much, end up taking fewer, not more, vacation days.

So perhaps the answer isn't to shoot for the stars and go with a trendy "anything goes" vacation policy, but instead just to offer a bunch more days. Not only will you experience the satisfaction of no longer being a disgrace in the eyes of Richard Branson, but your people will thank you and your bottom line is likely to rise too.