Is the 21 million bitcoin limit unchangeable?

[lleibowitz]

I remember that Gavin said he worried about a fork when block reward drops from 50 to 25 coins last winter, since there was someone coded a client with 50 coins reward forever. But it seems that fork had some technical problems and was not able to maintain the stable block generation, so it ended without many people knowing of it

Time is on our side here. The longer bitcoin is in existence (and the larger the userbase gets) the more unlikely it is for a fork to gain momentum.

[RodeoX]

I remember that Gavin said he worried about a fork when block reward drops from 50 to 25 coins last winter, since there was someone coded a client with 50 coins reward forever. But it seems that fork had some technical problems and was not able to maintain the stable block generation, so it ended without many people knowing of it

Time is on our side here. The longer bitcoin is in existence (and the larger the userbase gets) the more unlikely it is for a fork to gain momentum.

I'm glad this fell apart. I would certainly have traded my bitcoin for gold at that point. I would also consider the project dead.

[markm]

Basically they just wanted GRouPcoin but with all their bitcoins magically already on the GRouPcoin chain waiting for them. They can still go buy GRouPcoins if they still think 50 coins per block forever is doubleplus good.

-MarkM-

[MoonShadow]

Forcing a hard fork in order to alter some aspect of the network doesn't even mean that you'll succeed in altering your desired aspect, but the resources required to fight the good hard fork fight are quite high, and completely unrecoverable.  Yet, if a minority of users and miners decide to make that fight, there will be a blockchain fork, and the majority of the losses will fall upon the minority group until they can either muster up the resources to dominate the network or quit the fight and take their balls and go home.

It's not necessary to be a fight, two forks can co-exist since they serve the different interest from different users, its just those pre-fork coin can be spent on both fork, and it benefit the early adopters again (Pre-fork coins will worth more, people will try to get as much coin as possible before a fork happened  )

It's not necessary, but both chains can't coexist unless one changes certain network parameters, such as port number.

So, theoretically, all that is needed to change the 21 M BTC limit is to get everyone to agree to that change; but that isn't something that is up for debate here.  No matter who or why, there is no way that a consensus to change that metric in Bitcoin is going to happen without a blockchain fork; and it would be a harsh fight.  That number isn't so arbitrary, unlike the max_blocksize rule.

It does not matter it is MAX_BLOCK_SIZE or nSubsidy, as long as they can be changed through a software upgrade, there is a POSSIBILITY that a future software upgrade will change some bitcoin characters. This possibility is the biggest risk and uncertainty of bitcoin

I concede that the possibility exists.  That's different than claiming that it's a non-trivial risk.

[TierNolan]

That's not quite true. Version 1.0 didn't have a 1MB limit, but instead used the same 0x2000000 byte, or 32MiB limit, used for any serialized data. Satoshi later added MAX_BLOCK_SIZE so that miners wouldn't create blocks bigger than 1MB, but larger was still accepted.

That is interesting.  It sets a "harder" max block size, even if the 1MB limit is increased.

To increase the limit beyond 32MB, it would be necessary to change the message structure, or allow blocks to be split over multiple messages.

The commit comment is deliberately misleading: "only accept transactions sent by IP address if -allowreceivebyip is specified"

Any reason to make them misleading?  It would seem like a recipe to making alt-clients incompatible.

[johnyj]

It's not necessary, but both chains can't coexist unless one changes certain network parameters, such as port number.

Yes I remember that 50 coin's chain fork client somehow detected blocks from the bitcoin original chain and that made it stop to work

It does not matter it is MAX_BLOCK_SIZE or nSubsidy, as long as they can be changed through a software upgrade, there is a POSSIBILITY that a future software upgrade will change some bitcoin characters. This possibility is the biggest risk and uncertainty of bitcoin

I concede that the possibility exists.  That's different than claiming that it's a non-trivial risk.

If bitcoin has gained mainstream acceptance, and some powerful entity like CIA decided to change these rules, it will be much easier than when these rules were hard coded in the blockchain itself. They just need to ask a software company to bake the US government version of bitcoin client and push it into major exchanges

At least they will debate why these rules can not be changed, that will take lots of macro economic related discussion

[codro]

No. Why bother with Bitcoin, go enjoy some other inflationary currency. Bitcoin is one of the few non-inflationary currencies in existence. Can people who want a non-inflationary currency have a few options for a change?

Not all of us believe that constant consumption is the key to a prosperous future. What we don't need today can be saved for tomorrow.

Perpetually inflating crypto-currencies exist. Use those. OK?

Let's assume Bitcoin is the only currency in existance and your salary is paid in it.

As global population grows, your salary will get smaller and smaller from month to month. Your general purchasing power should stay the same because prices should also drop.

However, what is the logic supporting this? Hoarding is extremely encouraged, because you are assured to buy a lot more tomorrow than today with the same amount of money. Your savings never devalue, but they tremendously value.

Why should money that doesn't circulate and isn't used for anything at all (investments, development, etc) gain value simply by not being used?

Please explain this. The way I see it is that it simply promotes laziness and is detrimental to any future growth.

I hope people come to their senses and realize that at least the same inflation as gold (2%) is actually required in the long term. Luckily, we have until 2024 to get this changed, until then inflation in Bitcoin is going to be >2%. We want Bitcoin to succeed, not some other crypto-currency - it should be an easy enough flaw to fix.

Nothing is limited in our world or in nature, except perhaps atoms in the Universe. If we ever run out of valuable minerals on Earth, we will mine asteroids and other planets. Having a hard limit on one side (currency) and a variable on the other (population, economy, resources) doesn't make any sense. Ideally they should be in perfect synchronicity.

[justusranvier]

Why should money that doesn't circulate and isn't used for anything at all (investments, development, etc) gain value simply by not being used?

Please explain this. The way I see it is that it simply promotes laziness and is detrimental to any future growth

In order to accumulate savings, a person must consume less than he produces. The increase in future purchasing power is the reward for loaning his productivity into the economy, allowing other people to consume his surplus production in his place because they could generate further productivity with it.

That's the exact opposite of encouraging laziness. Hard work and deferred gratification are what is rewarded.

[maxmint]

Let's assume Bitcoin is the only currency in existance and your salary is paid in it.

As global population grows, your salary will get smaller and smaller from month to month. Your general purchasing power should stay the same because prices should also drop.

However, what is the logic supporting this? Hoarding is extremely encouraged, because you are assured to buy a lot more tomorrow than today with the same amount of money. Your savings never devalue, but they tremendously value.

Why should money that doesn't circulate and isn't used for anything at all (investments, development, etc) gain value simply by not being used?

Please explain this. The way I see it is that it simply promotes laziness and is detrimental to any future growth.

I hope people come to their senses and realize that at least the same inflation as gold (2%) is actually required in the long term. Luckily, we have until 2024 to get this changed, until then inflation in Bitcoin is going to be >2%. We want Bitcoin to succeed, not some other crypto-currency - it should be an easy enough flaw to fix.

Nothing is limited in our world or in nature, except perhaps atoms in the Universe. If we ever run out of valuable minerals on Earth, we will mine asteroids and other planets. Having a hard limit on one side (currency) and a variable on the other (population, economy, resources) doesn't make any sense. Ideally they should be in perfect synchronicity.

Here's another way of viewing this: If bitcoin was the only currency then your savings purchasing power could actually decline over time. Today we have 11 million coins and I have 100 btc in my savings, so I own x% of the all bitcoins. In a couple of years from now I will own less than x% of all bitcoins as there are new coins coming into existence.

[codro]

Purchasing power won't decline over time because prices drop at at least the same rate. If a chicken costs 100 btc today, or x% of all bitcoins, as more people are trading more chickens prices will drop from two reasons: 1) increased supply 2) deflation. So it will cost 1 BTC Z time from then, or .x% of all bitcoins.

[codro]

In order to accumulate savings, a person must consume less than he produces. The increase in future purchasing power is the reward for loaning his productivity into the economy, allowing other people to consume his surplus production in his place because they could generate further productivity with it.

That's the exact opposite of encouraging laziness. Hard work and deferred gratification are what is rewarded.

Unfortunately - while idealistic, that's not realistic. It's going to simply be a matter of age.

Someone just going into the workforce will be making a fraction of what their parents made when they were young. Money will not move and production will cease resulting in bankruptcies and unemployment.

And, constantly decreasing salaries and prices would also be a logistical nightmare.

[justusranvier]

Unfortunately - while idealistic, that's not realistic. It's going to simply be a matter of age.

Someone just going into the workforce will be making a fraction of what their parents made when they were young. Money will not move and production will cease resulting in bankruptcies and unemployment.

And, constantly decreasing salaries and prices would also be a logistical nightmare.

You're right - savings must constantly be devalued because central planners always know best how individuals should balance immediate vs deferred consumption.

I recommend you never buy any bitcoins.

[codro]

Unfortunately - while idealistic, that's not realistic. It's going to simply be a matter of age.

Someone just going into the workforce will be making a fraction of what their parents made when they were young. Money will not move and production will cease resulting in bankruptcies and unemployment.

And, constantly decreasing salaries and prices would also be a logistical nightmare.

You're right - savings must constantly be devalued because central planners always know best how individuals should balance immediate vs deferred consumption.

I recommend you never buy any bitcoins.

Seriously? Where did you read that I said that savings must be devalued? This is the problem with these forums, too many zealots with their fixed ideas.

[justusranvier]

Seriously? Where did you read that I said that savings must be devalued?

Here:

Why should money that doesn't circulate and isn't used for anything at all (investments, development, etc) gain value simply by not being used?

The only way to prevent savings from gaining value is to dilute, i.e. devalue, them with new currency units.

This is the problem with these forums, too many zealots with their fixed ideas.

Oh, so we're name-calling now? I can play that game too.

The problem with online liars is they act all surprised that people fail to forget what they said a few posts before.

[codro]

So in your opinion there are two options here:

A) ridiculously valuing savings for no reason
-or-
B) devaluing savings


C) maintaining constant value

How about C because it might make more sense? No? Okay. Online liars, good one.

[Peter Todd]

That's not quite true. Version 1.0 didn't have a 1MB limit, but instead used the same 0x2000000 byte, or 32MiB limit, used for any serialized data. Satoshi later added MAX_BLOCK_SIZE so that miners wouldn't create blocks bigger than 1MB, but larger was still accepted.

That is interesting.  It sets a "harder" max block size, even if the 1MB limit is increased.

To increase the limit beyond 32MB, it would be necessary to change the message structure, or allow blocks to be split over multiple messages.

Not really. The 32MiB limit on serialized messages is just an anti-DoS attack measure. There isn't anything inherent in the serialized messages themselves that limits them to 32MiB; to make >32MiB blocks just requires both numbers to be changed at once. That said you are correct in that allowing blocks to be split over multiple messages will happen, if only because sending a block can be faster because you can skip sending the transactions if the receiver already knows about them.

The commit comment is deliberately misleading: "only accept transactions sent by IP address if -allowreceivebyip is specified"

Any reason to make them misleading?  It would seem like a recipe to making alt-clients incompatible.

Satoshi was solidly against the development of alt-clients, even just to spend coins let alone mining. That said those were very early days and he probably wanted the flexibility to change things as Bitcoin's core evolved, and it did. There is some really kooky code from those days in the repository though; did you know Satoshi wrote the beginnings of an EBay like auction market and put it in the client itself?

[MoonShadow]

No. Why bother with Bitcoin, go enjoy some other inflationary currency. Bitcoin is one of the few non-inflationary currencies in existence. Can people who want a non-inflationary currency have a few options for a change?

Not all of us believe that constant consumption is the key to a prosperous future. What we don't need today can be saved for tomorrow.

Perpetually inflating crypto-currencies exist. Use those. OK?

Let's assume Bitcoin is the only currency in existance and your salary is paid in it.

I stopped reading right here.  This assumption makes any comparison to bitcoin invalid.  Bitcoin was not invented either within such an enviornment nor in order to create such an environment.  Your argument is invalid.

[Sunny King]

Satoshi was solidly against the development of alt-clients, even just to spend coins let alone mining. That said those were very early days and he probably wanted the flexibility to change things as Bitcoin's core evolved, and it did. There is some really kooky code from those days in the repository though; did you know Satoshi wrote the beginnings of an EBay like auction market and put it in the client itself?

Very interesting. What happened to these code for the beginnings of bitbay?

[archaeopteryx]

So there's this magical limit of ~21 million bitcoins that can theoretically exist at max. Many assumptions about the future of bitcoin are based on this number.

How easy / hard would it be to change this limit? It seems, this function controls how many coins are given to miners for solving a block. If developers decided to change this function, the 21 million number would change too, right? Or is the 21 million number somehow coded deeper in the system?

I'm still working through understanding the Bitcoin protocol, but there's also these lines

Code:

/** No amount larger than this (in satoshi) is valid */
static const int64 MAX_MONEY = 21000000 * COIN;
inline bool MoneyRange(int64 nValue) { return (nValue >= 0 && nValue <= MAX_MONEY); }

from the main.h file. I'm not sure what exactly this limits, (the amount of BTC in a single account, the amount of BTC in a transaction?) and would be curious if a more advanced programmer could explain it to me. This probably isn't considered to be coded any "deeper" in the system, as it's not something stored back in an early block, but it seems to be some other kind of constraint on the number of coins.

[Sunny King]

21000000 * COIN is the theoretical upperbound of bitcoin's entire money supply. Of course no one account or transaction can have more than that number, so it is used to check that a given money value is within the valid range.

To understand how this limit came about, you need to understand the function GetBlockValue() that give rise to the upperbound of 21M * COIN: MAX_MONEY = 2 * 210000 * 50 * COIN

Code:

int64 static GetBlockValue(int nHeight, int64 nFees)
{
    int64 nSubsidy = 50 * COIN;

    // Subsidy is cut in half every 210000 blocks, which will occur approximately every 4 years
    nSubsidy >>= (nHeight / 210000);

    return nSubsidy + nFees;
}