"This document should take about 2 hours." You start with that estimate, only to find half a day has passed. "I'll finish it by the end of the week," you say, yet the work slips into the following Monday. To be honest, this is a failure I have repeated many times myself.
The strange thing is that this isn't the kind of mistake that "gets fixed once you fail." No matter how many years we work, we continue to underestimate time in the same way and overshoot our deadlines just the same.
In fact, a psychologist identified the structure of this phenomenon nearly half a century ago. It was Daniel Kahneman, who would later win the Nobel Prize in Economics.
We Ignore Our Own Past When Estimating
In 1979, Kahneman, along with Amos Tversky, proposed the "Planning Fallacy." This is a cognitive bias where people estimate the time required for a task optimistically, ignoring their past experience with similar tasks.
There is a famous empirical study. In a 1994 study by psychologist Buehler and colleagues, university students working on their theses were asked to predict how many days it would take to finish.
The average prediction was 33.9 days. The actual time taken was an average of 55.5 days. That is an overshoot of over 60%. Furthermore, even their "worst-case scenario" pessimistic predictions (averaging 48.6 days) failed to match reality. We remain optimistic even when we try to imagine the worst.
The cause is clear: when planning, people only construct the "ideal scenario for this time" and fail to reference their own past data, such as "it took twice as long last time." That is why we miss the mark every single time.
Work Expands to Fill the Time Available
There is another structural reason for overshooting estimates. It is "Parkinson's Law," pointed out by British historian Parkinson in the 1950s.
Work expands so as to fill the time available for its completion.
If you reserve a whole day for a task that could be finished in 2 hours, for some reason, it takes the whole day. The extra time is absorbed by the expansion of the work itself.
When people feel they have "plenty of time," they tend to consider various options and engage in repeated trial and error. As a result, they aim for 100 points on a task where 60 points would have sufficed, and end up missing the deadline. Or, they exhaust themselves in the process of aiming for 100 points, which actually lowers the quality.
This is because as options and decision-making opportunities increase, "hesitation" arises, wearing down decision-making energy (willpower). Research by social psychologist Baumeister and colleagues (1998–) also reports that repeated choices and self-control reduce persistence in subsequent tasks.
The more you think "I can do this and that," the less you can concentrate. Having extra time is not necessarily your ally.
Changing Results Just by "Segmenting" Deadlines
The countermeasure is simple: segment your time into short intervals. If you set a frame of, say, 15 minutes, the things you can do are naturally narrowed down. Concentration is higher under constraints than when you are free.
There is an experiment that supports this. In 2002, behavioral economist Ariely and colleagues assigned three reports to MIT students under different conditions:
- No deadlines: Submit all at once at the end of the semester.
- Self-imposed deadlines: Students set their own (with penalties for missing them).
- Mandatory deadlines: Submission dates were evenly spaced and dictated.
The best grades came from the "Mandatory deadlines" group, followed by "Self-imposed," and the lowest were from the most flexible "No deadlines" group. Segmented deadlines prevented procrastination and improved performance.
When a deadline like "leaving the office on time" is set, you become conscious of the workload and time available, narrowing your options. Hesitation decreases, the waste of willpower is reduced, and concentration increases. Even within the same amount of time, this leads to higher-quality results.
It is often said, "If you want something done, ask a busy person," and it follows the same logic. Busy people are accustomed to the rhythm of concentrating within time constraints, allowing them to handle two or three times the workload of others in the same amount of time.
Three Actions You Can Take Today
1. Base estimates on "past performance"
Instead of an ideal scenario, estimate based on the actual results of similar past tasks. If it took 4 hours last time, it will take 4 hours this time. The thought that "I should be able to do it faster this time" is usually a betrayal.
2. Break deadlines into smaller pieces
Instead of "finishing everything at the end," set "multiple deadlines in the middle." For a week-long task, set 2–3 intermediate checkpoints. Even self-imposed deadlines are far more effective than none at all.
3. Segment the work time itself
Start by deciding on a frame of 15 or 30 minutes. Thinking "I'll start after I've secured plenty of time" might be walking straight into the trap of Parkinson's Law.
Conclusion
Missing deadlines is not due to a lack of will or ability, but rather a common human cognitive habit. Since it is a habit, it cannot be fixed by sheer willpower. What needs to be reviewed is the system.
Estimate based on past performance, break down deadlines, and segment time into short intervals. Constraints are not a symbol of lack of freedom, but a device for generating focus—just by reframing it this way, your relationship with time should begin to change.
I hope this article is of some help to you. Thank you for reading to the end. @mmmsumo
References
- Kahneman, D., & Tversky, A. (1979). Intuitive prediction: Biases and corrective procedures. TIMS Studies in Management Science, 12, 313–327.
- Buehler, R., Griffin, D., & Ross, M. (1994). Exploring the "planning fallacy". Journal of Personality and Social Psychology, 67(3), 366–381.
- Ariely, D., & Wertenbroch, K. (2002). Procrastination, deadlines, and performance. Psychological Science, 13(3), 219–224.
- Baumeister, R. F., et al. (1998). Ego depletion: Is the active self a limited resource? Journal of Personality and Social Psychology, 74(5), 1252–1265.
- Parkinson, C. N. (1957). Parkinson's Law: The Pursuit of Progress. John Murray.
