*"The United Nations will be celebrating its 70th anniversary in 2015. That event must be grasped as an opportunity to advance the idea."* [

source]

Mankind has a certain fixation with multiples of 10 [and 5]. We celebrate 10th, 20th, etc., anniversaries more than, say, the 4th or the 17th anniversary. This is not rational. Just because a number happens to be the multiple of 10 doesn't make it any extra special or significant or meaningful. 10 itself is just a number like every other number. Just because the number of digits increases at 10 doesn't mean that it is any extra wise or logical or useful to celebrate the 10th anniversary of something more than celebrating, say, the 8th anniversary. Similarly, it isn't any extra wise or helpful to plot and analyze the profitability of a firm over a 10 or 15 year period, than it is to perform the same activity over, say, 12 or 17 years [or 12 or 16 years, to avoid suggesting a "clean" interval of 5 years].

There's nothing any extra significant about the 70th anniversary of the UN than it is about the 69th anniversary.

We must also remember that it is only because we use the decimal number system that we encounter addition of digits at multiples of 10, 100, etc. Also, it's only because of this base-10 system that we get this clean look with all zeroes often - 10, 20, 50, 100, 500, etc. Had we been using a base-7 or a base-16 number system, our "special" numbers would've been completely different [for example, what is 16 in our base-10 number system would've been equivalent to our 10 in a base-16 number system], implying that considering 10 to be any extra special is a mistake and not rational.

**Update [11-Nov-15]:** Leahy's statement that "year-end is essentially an arbitrary point" is just another way of looking at the above thought.

**Update [11-Sep-16]:** Similarly, the "great"

700 score barrier for GMAT is rather arbitrary. Why did this so-called

"important threshold" have to be a

multiple of 100? Why wasn't it 690 or 710? This is because we're

just obsessed with thinking/working in terms of "easy" numbers that are multiples of 10, 100, and so on, rather than working with exact and genuinely critical/useful values which will most likely be "weird" numbers.

Similarly, the claim that

150 hours worth of preparation is ideal for GMAT is another example of our fixation with clean, simple numbers that are multiples of 5/10/20/50/100. Suppose the actual, optimal number of hours is 136, then it means that we're unnecessarily making folks waste 14 hours because we're trying to dish out a simple number.

Similarly, the claim that chewing food 32 times results in complete/proper digestion seems fake, because why would the right number of chews have to be 32, the number of teeth in an adult human? It just seems like someone picked the number of teeth and assigned the same "easy" and "related" number as the optimum number of chews. Easy doesn't necessarily mean the best or optimal.

**Update [17-Oct-16]:** Vehicle manufacturers ask you to get the vehicle serviced at 5,000 or 10,000 km [VW asks at 15,000]. Why did these numbers have to be multiples of 5,000? Couldn't these have been "weird" looking numbers like 6,000, or 9,000, or 13,000?

**Update [24-Mar-17]:** Why are estimates about number of

stars or

galaxies expressed in terms of powers of 10? Why aren't these expressed as powers of 2, 3, 5, 7 or 8? Is the number 10 something special compared to other numbers? Is it "simpler"? Does expressing as powers of some other number make the estimate less accurate [the reverse could actually be true]?

**Update [4-Aug-18]**:

Every little man is having a collective orgasm now that Apple has become the first "1 trillion dollar" company [actually it was PetroChina, but let's leave that for now]. So what, I ask? Has it become "1 trillion euro" or "1 trillion pound" company? And if it does that one day, will that be a reason for another collective orgasm(s)? What's the significance of touching the undoubtedly clean-looking number 1,000,000,000,000 on the US dollar line? Was Apple's success any less when this figure was, say, 999,999,998,557? Ordinary men have this fixation with so-called "special" numbers. Apple

had already achieved what is being celebrated now when it had touched the 999,999,998,557 number. And why is this particular number more important on the USD line, but not so relevant on EUR or GBP or CNY lines? Who decides what number is more important than the other, and why?