This article originally appeared on HBR.org. 

High human capital productivity — one key to great financial results — requires hiring the right people, teaming them effectively, and eliminating organizational barriers to high performance. It also requires paying close attention to how people in the organization interact. At many companies, they’re spending way too much time answering emails and attending unproductive meetings.

Why should this be? Blame Metcalfe’s Law.

Robert Metcalfe’s famous dictum states that the value of a network increases geometrically with the number of connected devices. One fax machine is worthless; a million fax machines create a valuable network. But the law has a dark side: as the cost of one-to-one and one-to-many interactions declines, the number of these interactions increases dramatically. And people are interacting more than ever. They are sending scores of emails every day. They are copying many of their colleagues, whether or not those individuals really need to see the message.

Worst of all, they are calling meetings. In the past, organizing a meeting of executives was time-consuming and therefore expensive; assistants had to spend hours on the phone finding times that worked for attendees. Now all they need to do is check Outlook or a similar program and send a quick email. As a result, most executives are spending 20 hours or more every week in meetings. And one meeting usually spawns many more. For example, my colleagues and I found that a single weekly executive committee meeting at a large company generated about 300,000 hours of preparation time each year (the equivalent of nearly 150 full-time-equivalent employees).

But meetings don’t have to get the best of you. You can manage them as closely as you manage every investment. There are four keys:

1. Don’t hold a meeting for the sake of holding a meeting. Meetings are great for some tasks, like gathering input and coming to a group decision. They aren’t so good for other tasks, such as drafting a strategy document. Before calling a meeting, decide whether it’s really the best way to get the job done.
2. Manage the invite list. In many companies it’s bad form not to invite lots of people to a meeting. What people don’t realize is that every additional attendee adds cost. Unnecessary attendees also get in the way. Remember the Rule of 7, which states that every attendee over seven reduces the likelihood of making a good, quick, executable decision by 10%. Once you hit 16 or 17, your decision effectiveness is close to zero.
3. Change the default time on meetings. Not too long ago, most companies called 30-minute meetings. Now the typical default time has grown to 60 minutes, even though every additional minute generates more cost. As my colleagues and I recently noted in HBR, one company established a rule: if a meeting was to last more than 90 minutes, it required approval by an executive two layers up from the convener. This rule quickly cut meeting time.
4. Improve the effectiveness of every meeting minute. You can boost meeting effectiveness through some simple disciplines. Clarify the purpose of every meeting. Spell out people’s roles in decisions. Create a decision log that captures every decision made in a meeting. (If the log is blank, you’ll find that people begin questioning why the meeting was held at all.)

Recently, my colleagues and I heard a story about a U.S. undersecretary of defense who was managing procurement. She came to her first meeting with contractors and saw some 60 people in the room. So she said, “Let’s first create a big circle. We’ll go around the room, and everyone can say who they are and why they’re here.” Participants rolled their eyes — did they really have to do something this gimmicky? — but did as she asked.

After the first two had identified themselves, the undersecretary said, “Thanks for your interest, but we won’t need you here. You can excuse yourself.” Others met a similar fate. By the time she got to the 10th person in the circle, people all over the room were getting up to leave, knowing they had no real reason to be there. Eventually the group got down to around 12 members — and the human capital productivity of that meeting rose about fivefold.

So Metcalfe’s Law cuts both ways. Capitalize on its value, by all means, but watch out for the costs hidden in its dark side.

Michael C. Mankins is a partner at Bain & Company. He is based in San Francisco and heads Bain's Organization Practice in the Americas.