Well some arbitrary number had to be chosen. Might as well make it 21 million 

Remember bitcoins can be divided up into really small fractions!

I seem to recall someone quoting Satoshi saying it was "an educated guess".
Whatever that means.

I also don't understand the reasoning. If you're serious about a currency becoming a major player in the world, you'd at least try to keep the expected single unit value in the same order of magnitude as existing currencies. That's also what was done with the €. Once it exists it will lead its own life and establish natural exchange rate levels, but 21M can never do that.

In any case, we can always correct it. Just create a new currency, which is not minable, but only obtainable by exchanging BTC. The BTC that is exchanged will be lost from the Bitcoin circuit.

You could think of multiple coexisting virtual currencies, each based on its own economical model.

We can fix it just by changing the capitalization. Just as 1 calorie is 4.814 joules but 1 Calorie is 4,814 joules, if at some point in the future, 4.814 BitCoins is a fortune, we can call it 4,814 BiTcoins.

Why 21 million specifically? I want to imagine that it's some nice fraction of the USD value of the money supply of all world currencies (21 trillion? glancing at Wikipedia) give or take. So if the value of the Bitcoin economy was valued at 1-ten thousandth of all existing currencies, it would trade at .01 USD, which looks good enough for it to be on par with the Yen and other currency's exchange rate and give it the potential to be taken seriously as a currency. And one-ten thousanth seemed very possible on the low end, so 21 million was decided. Complete guess.

Keep in mind that "a Bitcoin" doesn't exist in any real sense in the code. What does exist is the satoshi (.00000001 BTC). In other words, there's not really such a thing as 21 million Bitcoins. Rather, in the technical sense there are 21x10^6*10^8=2.1x10^15 = 2.1 quadrillion satoshis. In comparison, according to Google, the world GDP is about $56 trillion, which is to say about 5.6 quadrillion pennies. (Yes, I know the whole world GDP is not actually measured in dollars, but go with me here.) So really, it's not that ridiculous a level of volume.

a little over a year ago one bitcoin was worth just $0.006   (see laszlo's pizza as evidence)

here's why that is relevant:

unfortunately most people don't grasp the basics.  ask someone around you this question:
  right now general motors stock (nyse:gm) is trading at $30 a share
  ford (nyse:f)  is trading at $14 a share.
  which company is "better" (or "worth more").

if the answer comes back gm, now you know why 21 million bitcoins was the perfect number.  

notice when bitcoin's "tipping" point started.  about the time it hit parity with the dollar.  too many people think bitcoin is superior because it trades more than a dollar.  not that i don't agree bitcoin is superior, but that comparative value should hardly be a factor.

(incidentally, ford's market cap at $51 billion is greater than gm's at $47 billiion.  but that doesn't matter, as the only correct answer to the "which is better" question is "don't know, how many shares are there?")

Why Satoshi chose 21? Dunno. Could be as explained above. But this is interesting: http://www.ridingthebeast.com/numbers/nu21.php

Includes things like

• Number of the perfection by excellence, 3 x 7, according to the Bible.
• Symbol representing the unknown superiors or the great spiritual Masters of the humanity.

It's easy, all you have to do is google it....


Search Results

Immigration increases Australian population - 21,000,000

I would've gone with '42', in tribute to Douglas Adams