Most investment bankers I know work terribly long hours. Ten to twelve to fourteen hour days. Sometimes more. And sometimes it's not even work, because according to a 2010 study published in Human Relations that's how your boss and colleagues judge you.

A group of researchers led by professor Kimberly Elsbach conducted a series of interviews of 39 corporate managers and found that they generally consider their employees who spent more time in office to be more dedicated, hardworking and responsible. Let's throw in words like passionate in as well.

But it turns out, this mindset is wrong when applied to today's professionals. The value of what professionals do isn't the time they spend, but the value they create through their knowledge.

Working longer hours, employees tend to impede the development of productive habits, and by focusing on hours worked instead of results produced, how is this the best possible way to use an employee's time?

One good example are business meetings. Most people would agree that meetings are a waste of time, simply because most of them are too long, too large and too unfocused.

Consider one manager's description of an employee, as reported in Elsbach's study:

"So this one guy, he's in the room at every meeting. Lots of times he doesn't say anything, but he's there on time and people notice that. He definitely is seen as a hardworking and dependable guy."

He was praised simply because he attended the meeting, not for the value that he added to it.

In research published in HBR in 2006, Sylvia Ann Hewlett and Carolyn Buck Luce reported that 62 percent of high-earning individuals in America (whom they define as the top 6% of earners) work 50 hours or more per week; 35 percent work 60 hours or more per week.

And as any white collar worker in almost anywhere will tell you, this applies to a lot of professionals everywhere.

So how do you work less hours but be more productive?

First, you'll have to start by evaluating your use of time. Know what's important to you, and what's not important. Here are a few things:

Decline meetings, whenever you can.To be polite, you can explain your workload and request to see the meeting's minutes instead.

Don't be afraid to use the "delete" button when reviewing your inbox.

If you can't say "no" to a certain request, recognize that it may only require a B effort. Don't spend hours bumping it up to an A unless you really need to.

Of course, this is from an employee point of view, but it will help a lot if organizations enforced this. Work smarter instead of longer. You'll save more time, effort and money.

[Harvard Business Review]