As of yesterday, summer has officially begun. That means warm days, long evenings ... and empty offices. The hot months might be prime time for enjoying the great outdoors, but as any boss (or worker distracted by daydreams of an upcoming getaway) can tell you, vacation season is not known to be an exceptionally productive time of the year.

If you're a business leader, should you fight this reality or embrace it? And if you're an employee, should you feel guilty about getting less done because of summer time off?

A drumbeat of studies provides a pretty definitive answer to these questions. Employees' summer slacking, data shows, actually helps them get more done overall. So if your goal is maximum productivity over the medium and long haul, long summer vacations beat trying to corral sun-dazzled employees into working hard all season long.

The research-backed benefits of serious summer slacking

The latest survey to be tossed on top of this teetering pile of research is a poll of 1,000 American workers from employee rewards company O.C. Tanner. The results illustrate just how much employees are refreshed by a long summer break of a week or more.

For instance, the firm found that 70 percent of employees who take at least seven days away claim to be "highly motivated to contribute to the success of the organization." Just 55 percent of those who took less than a week say the same thing.

There were similar large gaps in feelings of belonging and loyalty between employees who got a full week or more off, and those forced to get through the summer with only the odd long weekend break. In fact, of those who took a substantial vacation, 65 percent reported a strong desire to continue working at their organization in the coming year. For those who took less than a week's vacation, the number was 51 percent.   

It is probably not the most shocking news in the world that employees who have adequate time to recharge and refresh are more motivated and happy. But the fact bears repeating when something like 50 percent of Americans haven't taken a proper vacation all year and only 25 percent take all the time they're due.

Let them apply sunscreen!

Part of that may be down to our national workaholic ways, and part of it may be down to strapped finances, but at least some of the blame goes to unsympathetic bosses who still haven't gotten the memo that a little lost productivity in summer means way more work getting done overall.

Don't be one of those bosses. Employees' beach trips and BBQs might mean delayed meetings or empty chairs in the office this summer, but those vacations also mean less stress. And, as British organization psychologist Cary Cooper has pointed out, "numerous studies have established the association between stress and lower productivity."