There’s a good chance most of the problems in your life and work come down to insufficient slack. Here’s how slack works and why you need more of it.

Imagine if you, as a budding productivity enthusiast, one day gained access to a time machine and decided to take a trip back several decades to the office of one of your old-timey business heroes. Let’s call him Tony.

You disguise yourself as a janitor and figure a few days of observation should be enough to reveal the secret of that CEO’s incredible productivity and shrewd decision-making. You want to learn the habits and methods that enabled him to transform an entire industry for good.

Arriving at the (no doubt smoke-filled) office, you’re a little surprised to find it’s far from a hive of activity. In fact, the people you can see around seem to be doing next to nothing. Outside your hero’s office, his secretary lounges at her desk (and let’s face it, the genders wouldn’t have been the other way around.) Let’s call her Gloria. She doesn’t appear busy at all. You observe for half an hour as she reads, tidies her desk, and chats with other secretaries who pass by. They don’t seem busy either. Confused as to why Tony would squander money on idle staff, you stick around for a few more hours.

With a bit more observation, you realize your initial impression was entirely wrong. Gloria does indeed do nothing much of the time. But every so often, a request, instruction, or alert comes from Tony and she leaps into action. Within minutes, she answers the call, sends the letter, reschedules the appointment, or finds the right document. Any time he has a problem, she solves it right away. There’s no to-do list, no submitting a ticket, no waiting for a reply to an email for either Tony or Gloria.

As a result, Tony’s day goes smoothly and efficiently. Every minute of his time goes on the most important part of his work—making decisions—and not on dealing with trivial inconveniences like waiting in line at the post office.

All that time Gloria spends doing nothing isn’t wasted time. It’s slack: excess capacity allowing for responsiveness and flexibility. The slack time is important because it means she never has a backlog of tasks to complete. She can always deal with anything new straight away. Gloria’s job is to ensure Tony is as busy as he needs to be. It’s not to be as busy as possible.

If you ever find yourself stressed, overwhelmed, sinking into stasis despite wanting to change, or frustrated when you can’t respond to new opportunities, you need more slack in your life.

In Slack: Getting Past Burnout, Busywork, and the Myth of Total Efficiency, Tom DeMarco explains that most people and organizations fail to recognize the value of slack. Although the book is now around twenty years old, its primary message is timeless and worth revisiting.

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The enemy of efficiency

“You’re efficient when you do something with minimum waste. And you’re effective when you’re doing the right something.”

Many organizations are obsessed with efficiency. They want to be sure every resource is utilized to its fullest capacity and everyone is sprinting around every minute of the day doing something. They hire expert consultants to sniff out the faintest whiff of waste.

As individuals, many of us are also obsessed with the mirage of total efficiency. We schedule every minute of our day, pride ourselves on forgoing breaks, and berate ourselves for the slightest moment of distraction. We view sleep, sickness, and burnout as unwelcome weaknesses and idolize those who never seem to succumb to them. This view, however, fails to recognize that efficiency and effectiveness are not the same thing.

Total efficiency is a myth. Let’s return to Gloria and Tony. Imagine if Tony decided to assign her more work to ensure she spends a full eight hours a day busy. Would that be more efficient? Not really. Slack time enables her to respond to his requests right away, thus being effective at her job. If Gloria is already occupied, Tony will have to wait and whatever he’s doing will get held up. Both of them would be less effective as a result.

Any time we eliminate slack, we create a build-up of work. DeMarco writes, “As a practical matter, it is impossible to keep everyone in the organization 100 percent busy unless we allow for some buffering at each employee’s desk. That means there is an inbox where work stacks up.”

Many of us have come to expect work to involve no slack time because of the negative way we perceive it. In a world of manic efficiency, slack often comes across as laziness or a lack of initiative. Without slack time, however, we know we won’t be able to get through new tasks straight away, and if someone insists we should, we have to drop whatever we were previously doing. One way or another, something gets delayed. The increase in busyness may well be futile:

“It’s possible to make an organization more efficient without making it better. That’s what happens when you drive out slack. It’s also possible to make an organization a little less efficient and improve it enormously. In order to do that, you need to reintroduce enough slack to allow the organization to breathe, reinvent itself, and make necessary change.”

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Defining slack

DeMarco defines slack as “the degree of freedom required to effect change. Slack is the natural enemy of efficiency and efficiency is the natural enemy of slack.” Elsewhere, he writes: “Slack represents operational capacity sacrificed in the interests of long-term health.”

To illustrate the concept, DeMarco asks the reader to imagine one of those puzzle games consisting of eight numbered tiles in a box, with one empty space so you can slide them around one at a time. The objective is to shuffle the tiles into numerical order. That empty space is the equivalent of slack. If you remove it, the game is technically more efficient, but “something else is lost. Without the open space, there is no further possibility of moving tiles at all. The layout is optimal as it is, but if time proves otherwise, there is no way to change it.”

Having a little bit of wiggle room allows us to respond to changing circumstances, to experiment, and to do things that might not work.

Slack consists of excess resources. It might be time, money, people on a job, or even expectations. Slack is vital because it prevents us from getting locked into our current state, unable to respond or adapt because we just don’t have the capacity.

Not having slack is taxing. Scarcity weighs on our minds and uses up energy that could go toward doing the task at hand better. It amplifies the impact of failures and unintended consequences.

Too much slack is bad because resources get wasted and people get bored. But, on the whole, an absence of slack is a problem far more often than an excess of it. If you give yourself too much slack time when scheduling a project that goes smoother than expected, you probably won’t spend the spare time sitting like a lemon. Maybe you’ll recuperate from an earlier project that took more effort than anticipated. Maybe you’ll tinker with some on-hold projects. Maybe you’ll be able to review why this one went well and derive lessons for the future. And maybe slack time is just your reward for doing a good job already! You deserve breathing room.

Slack also allows us to handle the inevitable shocks and surprises of life. If every hour in our schedules is accounted for, we can’t slow down to recover from a minor cold, shift a bit of focus to learning a new skill for a while, or absorb a couple of hours of technical difficulties.

In general, you need more slack than you expect. Unless you have a lot of practice, your estimations of how long things will take or how difficult they are will almost always be on the low end. Most of us treat best-case scenarios as if they are the most likely scenarios and will inevitably come to pass, but they rarely do.

You also need to keep a vigilant eye on how fast you use up your slack so you can replenish it in time. For example, you might want to review your calendar once per week to check it still has white space each day and you haven’t allowed meetings to fill up your slack time. Think of the forms of slack that are more important to you, then check up on them regularly. If you find you’re running out of slack, take action.

Once in a while, you might need to forgo slack to reap the benefits of constraints. Lacking slack in the short term or in a particular area can force you to be more inventive. If you find yourself struggling to come up with a creative solution, try consciously reducing your slack. For example, give yourself five-minutes to brainstorm ideas or ask yourself what you might do if your budget were slashed by 90%.

Most of the time, though, it’s critical to guard your slack with care. It’s best to assume you’ll always tend toward using it up—or other people will try to steal it from you. Set clear boundaries in your work and keep an eye on tasks that might inflate.

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Slack and change

In the past, people and organizations could sometimes get by without much slack—at least for a while. Now, even as slack keeps becoming more and more vital for survival, we’re keener than ever to eliminate it in the name of efficiency. Survival requires constant change and reinvention, which “require a commodity that is absent in our time as it has never been before. That commodity—the catalytic ingredient of change—is slack.” DeMarco goes on to write:

“Slack is the time when reinvention happens. It is time when you are not 100 percent busy doing the operational business of your firm. Slack is the time when you are 0 percent busy. Slack at all levels is necessary to make the organization work effectively and to grow. It is the lubricant of change. Good companies excel in creative use of slack. And bad ones only obsess about removing it.”

Only when we are 0 percent busy can we step back and look at the bigger picture of what we’re doing. Slack allows us to think ahead. To consider whether we’re on the right trajectory. To contemplate unseen problems. To mull over information. To decide if we’re making the right trade-offs. To do things that aren’t scalable or that might not have a chance to prove profitable for a while. To walk away from bad deals.

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Slack and productivity

The irony is that we achieve far more in the long run when we have slack. We are more productive when we don’t try to be productive all the time.

DeMarco explains that the amount of work each person in an organization has is never static: “Things change on a day-to-day basis. This results in new unevenness of the tasks, with some people incurring additional work (their buffers build up), while others become less loaded, since someone ahead of them in the work chain is slower to generate their particular kind of work to pass along.” An absence of slack is unsustainable. Inevitably, we end up needing additional resources, which have to come from somewhere.

Being comfortable with sometimes being 0 percent busy means we think about whether we’re doing the right thing. This is in contrast to grabbing the first task we see so no one thinks we’re lazy. The expectation of “constant busyness means efficiency” creates pressure to always look occupied and keep a buffer of work on hand. If we see our buffer shrinking and we want to keep busy, the only possible solution is to work slower.

Trying to eliminate slack causes work to expand. There’s never any free time because we always fill it.

Amos Tversky said the secret to doing good research is to always be a little underemployed; you waste years by not being able to waste hours. Those wasted hours are necessary to figure out if you’re headed in the right direction.