The Planning Fallacy: Why We Overcommit And How to Stop

Picture this: You have a day packed with meetings and obligations. Then, your best friend asks you to go out to lunch. After examining your calendar, you find a 45 minute block around noon that could work. You would still need to drive to the restaurant, order as soon as you arrive, and then get back to the office by 12:45pm to prep for your next meeting.

We’ve all been in a scenario something like this in the past, right? We’re already scheduled to the max, but a juicy opportunity presents itself so we squeeze it in determined we can make it work. More often than not, it fails. We’re late to the next meeting, over the deadline, stuck in traffic, etc. If “to err is human,” it seems like “to overcommit” is human as well.

Although it’s probably obvious, it’s worth diving into why overcommitment should be avoided. First, it puts us in a situation where we overpromise and underdeliver. That’s certainly not the fastest way to the corner office. Second, we’re putting ourselves in a stressful situation. Comparing your calendar and todo list only to find out you have absolutely no time available to get it all done? Not fun.

Why do we do this to ourselves? Why do we overcommit to projects, events, meetings, and tasks in the first place? In order to understand answers to those questions, we first need to understand why we’re so bad at predicting the future. We’ll look at research from The Black Swan by Taleb, Stumbling on Happiness by Gilbert, and others to help us understand and more importantly, improve.

Why We’re So Bad at Predicting the Future

If I asked you whether or not you could predict the future, you would probably say “no.” Despite what we might think while we’re in Vegas or making a college football bet with friends, we don’t have a prescient understanding of future events.

Still, on a daily basis, we’re actually predicting the future in some ways. For example, when you make plans with your friends to go to the movies in a week, you’re predicting a few things. First, you’re assuming that you’ll still want to hang out with these people. Second, you’re predicting that you’ll still want to see the movie. Third, you’re predicting that you’ll want to leave your house and go to the movies at the designated date and time.

All three of those predictions happen automatically in the back of your mind. We don’t even realize that they’re happening. Yet, if you have ever made plans then despised your past self for making them when the time arrived, you have experienced the issues with our follies of future prediction. Let’s look at three reasons why these future predictions aren’t as accurate as we believe in the moment.

Warning: Future will likely be different than it appears.

In The Black Swan, author Nassim Taleb lays out three fallacies that make us poor future predictors. Two are applicable in our context.

First, we fail to take what he refers to as “forecast degradation” into account. “We do not realize the full extent of the difference between near and far futures.” When we’re asked to predict the future, we think it will look and feel a lot like the present. We fail to realize just how different today is from yesterday and the day before. In Stumbling on Happiness, author Daniel Gilbert refers to this as the “illusion of foresight.”

“We insist on steering our boats because we think we have a pretty good idea of where we should go, but the truth is that much of our steering is in vain—not because the boat won’t respond, and not because we can’t find our destination, but because the future is fundamentally different than it appears through the prospectiscope.”

– Stumbling on Happiness (p. 21)

It’s not obvious what the future will look like so we default back to something we do know—the past (and present). Then, we assume the future will look a whole lot like…today.

Second, we discount the randomness of the future. “The third fallacy, and perhaps the gravest, concerns a misunderstanding of the random character of the variables being forecast…these variables can accommodate far more optimistic—or far more pessimistic—scenarios than are currently expected,” Taleb explains. Just as you don’t expect that car wreck to clog up traffic on the highway when you’re headed to work in the morning, you don’t forecast major client meltdowns or computer crashes when looking ahead to next week.

Taleb refers to these events as “black swans.” They’re highly unpredictable and can have a disproportionate impact on future predictions.

This task won’t take that long…will it?

We often underestimate the time it will take to complete a task. We lowball the time requirement. Then, best of all, when we’re faced with the reality that our predictions were inaccurate and the task will actually take much longer, we blame external factors as to why we’re late.

“I was late to the restaurant, but it’s only because I was caught at every single red light.”

“I would’ve had this in on time except Tom needed my help with another project.”

This tendency to lowball time requirements and blame external factors is referred to as the Planning Fallacy. It’s easily illustrated in a study of college students. “In the study, researchers asked students (college) to estimate how long it would take them to complete a task they had been assigned. Many of the students did not finish in time. When asked why, the students blamed events outside of their control.”

According to Kahneman in Thinking Fast and Slow, one reason we fall prey to the Planning Fallacy is our tendency to make forecasts based on best-case scenarios. When we envision driving to dinner, we envision clear roads and all green lights the entire way. Similarly, when we set deadlines for big projects, we don’t stop to consider what will happen if someone else in the office needs our help or the offsite retreat that we’ll be pulled away for. Instead, we assume we’ll have a week of completely uninterrupted work to focus.

Future tasks are fuzzy.

Picture this scenario: Your boss approaches you on a Wednesday and asks for you to take on a big assignment. You do a mental check of what you have going on this week. It feels pretty busy, but next week looks all clear. You agree to tackle the project and have it finished in a week.

You can already imagine what’s likely to happen, right? You’re either going to pull some long days to deliver on time or you’re going to ask for an extension.

When we look at this week, we can clearly state out the tasks and events clogging up our calendar. Next week though? That’s fuzzy. According to a study on overcommitment, “Lacking knowledge of what specific tasks will compete for their time in the future, they act as if new demands will not inevitably arise that are as pressing as those faced today.”

If you were to ask me what tasks will compete for my time next week, I would have a hard time listing them out. Since they’re hard to name, I just assume they don’t exist and I plan accordingly. Then, when they pop-up, I’m surprised, overwhelmed, and overburdened.

Cures for Overcommitment and the Planning Fallacy

We’ve established some reasons why we’re bad at predicting the future. Unreasonable future assumptions, unrealistic time estimates, and fuzzy future tasks all make us susceptible to overcommitment. Here are some suggestions for how to deal with it.

Take an outside view.

In Thinking Fast and Slow, Kahneman details two aspects one can take when assessing a project. He calls these the inside and outside views.

The inside view is the one that all of us…spontaneously adopted to assess the future of our project. We focused on specific circumstances and searched for evidence in our own experiences.

– Thinking Fast and Slow, p. 247

The inside view involves looking at things like past work already completed and forecasting future deadlines as a result forgetting that, again, the future might be vastly different than it appears.

For example, let’s say you’re a teacher writing lesson plans for the upcoming school year. You have already put together a lesson plan for the first few weeks covering your favorite topics. Now, it’s time to finish out the rest of the semester. How long could this possibly take?

In this case, the inside view considers a few things:

  • It was easy to come up with the plan for the first few weeks (AKA your favorite topics). It should be similarly easy to finish the rest of the semester.
  • Thinking back to last year, it didn’t take too long to create the lesson plan. It probably won’t take that long this year.
  • You probably had all of the resources (book chapters, articles, links) for your favorite topics ready to go. Certainly though, it can’t be that hard to put together everything for the new topics you’ll cover in the remaining weeks.

For the inside view, you’re searching your own past experiences for evidence that supports your assumption that the task won’t take too long.

Kahneman refers to the opposite stance as the “outside view:”

Using such distributional information from other ventures similar to that being forecasted is called taking an “outside view” and is the cure to the planning fallacy.

– Thinking Fast and Slow, p. 250

In the outside view, you’re examining the experiences of others, historical averages, and other information not pertaining to your current situation or personal past experience. In our example, we could consider:

  • How long do our fellow teachers usually spend coming up with a lesson plan?
  • Considering the teacher that previously put this lesson plan together, did he or she give you any advice on how long it took?

Whereas the inside view is entirely contained in our own personal experience, the outside view considers events and information from outside our experience. Kahneman explains how you can use the two together:

The argument for the outside view should be made on general grounds: if the reference class is properly chosen, the outside view will give an indication of where the ballpark is, and it may suggest…that the inside-view forecasts are not even close.

– Thinking Fast and Slow, p. 248

In other words, you’ll typically come up with an inside view right away. Force yourself to consider an outside view to see flaws in your inside view. To bring this all together, here’s the mental dialogue that could take place when making a hypothesis about the time it would take to build a lesson plan:

“I think this should take me a day or two, a week at most. However, I know that fellow teachers in my department have been spending multiple weeks putting together their lesson plans on similar topics. I also know that the instructor previously teaching these topics warned me that they can be tricky to put together. My intuitive assumption of a week at most is probably wrong. This will likely take me several weeks to put together.”

Break down tasks into smaller points.

Here’s a confession – I’ve had the same todo item on my list for multiple weeks now, and I keep punting it off. The todo is pretty simple. We have an upcoming event for Drink for Pink, a local nonprofit I helped to start. I need to call some local restaurants and shops to see if they would be willing to give us some gift cards for the event. Pretty simple stuff. The issue with this task and why I continue to punt it will become clear quite quickly.

In Todoist, the task reads: “Call restaurants to get gift cards.” On the surface, this seems pretty simple. I just need to call a few places (say, five) and ask if I can stop by and grab the gift cards. If you think about it in detail though, I need to 1) Determine which places to ask looking at the location of the event and the surrounding businesses 2) Find their contact information 3) Make the calls 4) Stop by and pickup the gift cards.

The task reads like it might take only 5-10 minutes, but in reality, it’s probably going to take closer to 20-30 minutes without considering the last step of actually picking up the gift cards. Circling back to a term we used above, the task is “fuzzy.”

When we add tasks to our todo list, the general tendency is to lump everything together into one vague task:

  • Plan budget proposal
  • Write goals recap from Q2
  • Build materials for presentation

While this list might encapsulate the core of what we’re hoping to do, they’ll likely lead you to massively underestimate the time required in each scenario. On the surface, the tasks feel simple and straightforward. However, each one is built of smaller subtasks that remain fuzzy and unclear from looking at the large list.

When creating a todo list, you can create more accurate time estimates by clearly detailing out the steps required, and if necessary, allotting an estimated time requirement to each:

  • Plan budget proposal
    • Pull past sales and expenditures from this year (15 min)
    • Forecast sales for next year (30 min)
    • Build spreadsheet models for budget (30 min)
    • Translate spreadsheet to presentation slideshow (60 min)

When detailed out, you’ll have a much clearer estimate of how much time to block off on your calendar.

Build in a buffer.

This approach is pretty straightforward. Whenever you’re estimating the time requirement of a project, overestimate by 25-50%, often referred to as the Scotty Principle.1 This gives you a better chance of underpromising and overdelivering in the event that you can deliver the work on a more aggressive timeframe.

Simple. Straightforward. Effective.


  1. Fun fact: The Scotty Principle got its name from Montgomery Scott of Star Trek fame. 

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