People seem to have a preference for celebrating "big round numbers", like the 2,000 post in the forum (although the 10,000 post would probably be more "special" - but not the 10,234 post, so it's not strictly a magnitude bias). There are lots of examples of this. Sports stats are another: baseball players celebrate 3,000 hits, 500 home runs, and 20 wins. Football players 1,000 yard seasons, and so on.

Why do we prefer marking events that are round numbers?


3 Answers 3


There might be a simple answer to that,involving a cognitive ability essential for survival: pattern recognition.

In psychology and cognitive neuroscience, pattern recognition describes a cognitive process that matches information from a stimulus with information retrieved from memory.1 Pattern recognition occurs when information from the environment is received and entered into short-term memory, causing automatic activation of a specific content of long-term memory.


We simply do not have many non-rounded numbers memorised, so when we recognise a big, rounded number, we tend to celebrate the fact. That is simply how our brain is wired, to recognise patterns and feel comfortable with easily identifiable ones rather than with irregular figments of reality (or numbers, in this case).

Another element to that is the fact that

Recognizing patterns allow us to predict and expect what is coming. The process of pattern recognition involves matching the information received with the information already stored in the brain. Making the connection between memories and information perceived is a step of pattern recognition called identification. Pattern recognition requires repetition of experience.

In other words and specifically in this case, it is not easy to predict what is after 19675 at a glance, as we hardly recognise the number, but it is easier to predict what follows after 20000.

Interestingly enough, this specific oddity of our brain is being used in marketing. Have you ever gotten annoyed at the 2.99 or 2.98 price tags? Your brain has to make an effort to round it to 3 instead of rounding it to 2, because you recognise 2 easier in that sequence (it's there) whereas to get to 3 you would have to pay attention to the calculation while going through the shopping list and making sure the kid doesn't knock the toy stand over.


I might be wrong but it might have something associated with the numerical goals we acheive as children, young adults and grown up. For example, becoming 10 years of age is a sign of maturity, mainly due to the double digits it contains. This leads us (as children) to believe that we are that much closer to becoming adults. When people turn 40 or 50 they put a lot more pressure on them selves than they would have if that number was decreased a year or two. Maybe it's the obvious facts such as 50 is closer to 60 than 49 is?

Also, when we learn how to count, we don't necessarily stop at 3, or 7, 10 is usually the number that kids are first introduced to, and once they learn it get appraise from external figures.

Basically, our preffered simplicity for numbers may or may not reflect our own personal achievements during our childhood and other significant life experiences. I know for a fact that I wouldn't be as proud of running a 39.7K as I would have been for running a 40K, even though the difference is a tiny 0.3.

When we announce our achievements to others we say "I'm in the top 10 for my age in cross-country!", assuming we come 7th, top ten sounds like a greater acheivement, this is just me, others may have different opinions.

Growing up and being congratulated for our achievements by older family members and other adult figures for unspecified winnings might have an impact on our greater admiration of "rounded numbers". I'm not quite sure whether or not I explained my self very well but I hope you understand what I'm saying.

  • 2
    $\begingroup$ I think this is a really useful set of additional examples of the phenomenon that's being asked about, but I don't think this explains why we have this preference. However, it's a good reminder that we are exposed to this kind of behavior from a very early age, and in that sense in might be learned. However, this still leaves open the question of why 10, 100, etc.. in the first place. $\endgroup$
    – Josh
    Commented Jul 13, 2014 at 2:44
  • $\begingroup$ I would have to otherwise say that the simplicity of the numbers and ease of remembering them is what makes us favour them over numbers such as 325,234. It takes our brains less time and effort to remember them, since there is usually one number that we're forced to remember, (e.g. in 200, we would just remember the "2") and after that it's just a matter of how many zeros. Sorry I couldn't answer your question, although I'm glad I could help! @Josh $\endgroup$ Commented Jul 13, 2014 at 4:08
  • $\begingroup$ Those are rather weak arguments if you ask me. For example, aren't 16 (my sweet 16 in USA) and 18 (legal 'adult' age in many countries) even more important 'growing up' ages? The examples you give are simply more proof that the OPs question is worth asking, but does not answer it. $\endgroup$
    – Steven Jeuris
    Commented May 28, 2018 at 8:31
  • $\begingroup$ It may be a little weak to a degree @StevenJeuris, but Samir's contribution does give a plausible explanation. Yes, there are exceptions such as the 13, 16, 18 and 21 ages, but then there are exceptions to a lot of things. The main thing is the question is about rounded numbers. I would say that the age exceptions are social constructs which create the exception. $\endgroup$ Commented May 28, 2018 at 12:52

Because round numbers are easier than full numbers. For instance, $$10^9=1000000000$$ saves a lot, instead of $$997843863678632762767267863$$ I do not know how to give you a short description of this number.

  • 1
    $\begingroup$ Could you clarify: (1) easier in what sense? (2) Saves a lot of what? (3) Why is simplicity of representation appealing? $\endgroup$ Commented Jul 10, 2014 at 6:55
  • $\begingroup$ The reason simplicity of information is preferable is because a human brain takes in an enormous amount of sensory data at all times. It's impossible to process all data accurately, so in order to function, the brain must adopt heuristics that approximate analysis in a viable timeframe. Otherwise we could not react to our environment in a timely manner. Decimal representation of numbers is helpful in that sense because it allows you to represent an inconcievable number as "ten to the power of nine", for example. It connects billions to the ability to count on your fingers. $\endgroup$
    – lea
    Commented Jul 10, 2014 at 7:36
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    $\begingroup$ I think this is on the right track, but there are lots of numbers that I could represent simply that don't seem to fit the pattern. For example: $512$ is $2^9$, but not many people seem to care about the 512th instance of something. $\endgroup$
    – Josh
    Commented Jul 13, 2014 at 2:48
  • $\begingroup$ Binary systems are only really in use in mathematics and computer programming. Decimal systems are basically universal. I think you'll find that there are a lot of computer programmers who get excited about binary numbers, just as readers of Douglas Adams are more likely to get excited by the appearance of the number 42. $\endgroup$
    – lea
    Commented Jul 13, 2014 at 6:47
  • $\begingroup$ I agree that decimal systems are more widely used, which suggests that there is a learning component to this effect (rather than numbers that can be easily compressed in general). $\endgroup$
    – Josh
    Commented Jul 19, 2014 at 20:11

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