One of the chief characteristics of Bitcoin (BTCUSD) is its limited supply. Other forms of money, including fiat currencies, can be printed at will by central banks—i.e., they have unlimited supply.
Bitcoin inventor Satoshi Nakamoto capped the number of bitcoin at 21 million, meaning there will only ever be 21 million bitcoins in existence. On average, these bitcoins are introduced to the Bitcoin supply at a fixed rate of one block every 10 minutes. In addition, the number of bitcoins released in each of these aforementioned blocks is reduced by 50% every four years. By August 2021, 18.7 million bitcoins were available, leaving roughly 2.3 million to be mined. The supply limitation makes Bitcoin scarce and controls inflation that might arise from an unlimited supply of the cryptocurrency.
As Bitcoin reaches its capped supply, its economics will alter. The incentives for various members in its ecosystem, such as miners and traders, will change. For example, miners may rely less on block rewards and more on transaction fees to earn revenue and profits for their operations. The cryptocurrency's network will also transform, and its participants will be different from the retail traders that populate its current ecosystem.
However, given the cryptocurrency's relatively undeveloped ecosystem, it is difficult to predict with certainty the effect of Bitcoin reaching its capped supply.
- There are only 21 million bitcoins that can be mined in total.
- Bitcoin will never reach that cap due to the use of rounding operators in its codebase.
- As of Aug, 2021, 18.77 million bitcoins have been mined, which leaves roughly 2.3 million yet to be introduced into circulation.
- When Bitcoin reaches its supply cap, block rewards will vanish, and miners will depend on fees from transactions occurring on the cryptocurrency's network for revenue.
- Bitcoin's network may evolve from its current unfinished state to becoming a bridge for monetary transactions and trading.
- Bitcoin the cryptocurrency will have a defined identity in the financial ecosystem.
Will Bitcoin Ever Reach the 21 Million Cap?
Before delving into the implications of Bitcoin's 21 million cap, it might be interesting to consider the question of whether it will ever reach that figure. Based on the cryptocurrency's current codebase and mining process, some observers say that Bitcoin may fall just shy of the 21 million figure.
To recap, Bitcoin is "mined" by miners who solve cryptographic puzzles to verify and validate a block of transactions occurring in its network. Block rewards, consisting of a set number of bitcoins, are distributed to miners who successfully confirm a transaction block. The rewards are halved every four years.
When the cryptocurrency was launched, the reward for confirming a block of transactions was 50 bitcoins. In 2012, it was halved to 25 bitcoins, and it went down to 12.5 in 2016. In May 2020, miners stood to earn 6.25 bitcoin for every new block. Block rewards for Bitcoin miners will continue to be halved every four years until the final bitcoin is mined. Current estimates for mining of the final bitcoin put that date somewhere in February 2140.
The Bitcoin mining process provides bitcoin rewards to miners, but the reward size decreases periodically to control the circulation of new tokens.
According to Andreas M. Antonopoulos, author of a book about Bitcoin's workings, the 21 million figure is an "asymptotic cap" on the number of bitcoin in existence. In simple words, this means that, while it may reach very close to figure, the cryptocurrency will never reach that limit. This is because block rewards and Bitcoin supply are never expressed in exact terms. Bitcoin's code uses bit-shift operators—arithmetic operators used that round decimal points to the closest smallest integer in certain programming languages. Therefore, a total supply of 6.2589 bitcoins will be rounded out to the closest smallest integer, in this case 6.
While it makes calculations easier, the practice leads to losses in satoshis, Bitcoin's constituent units, during each block confirmation. One bitcoin is equal to 100 million satoshis. According to some, the final bitcoin block will be numbered 6,929,999, and the total supply at that time will be 20,999,999.9769 satoshis. Since bitcoin uses a bit-shift operator system, its algorithm will round off that figure to 20,999,999 and leave the cryptocurrency just shy of its 21 million targeted cap.
What Happens When All 21 Million Bitcoin Are Mined?
A consequence of Bitcoin not reaching its planned cap is that it leaves open the possibility that the cryptocurrency's network will remain functional for a long time after 2140. No bitcoins will be issued, but transaction blocks will be confirmed, and fees will become the primary source of revenue. Ultimately, Bitcoin's network may function as a closed economy, in which transaction fees are assessed much like taxes are.
Can the rewards be in satoshis instead of actual bitcoin? Such a practice is unlikely and would require a change in the cryptocurrency's protocol to take effect.
That said, it is difficult to predict the effects of Bitcoin almost reaching the overall supply promised by Satoshi Nakamoto. This is partly because Bitcoin's ecosystem is still undeveloped. The cryptocurrency was originally conceptualized as a medium of exchange but it has found more popularity as a store of value—an investing asset—instead. It is possible that Bitcoin's ecosystem and workings might undergo a transformation, similar to the one that has occured in its identity, between now and 2140.
Although there can only ever be a maximum of 21 million bitcoins, because people have lost their private keys or have died without leaving their private key instructions to anybody, the actual amount of available bitcoins in circulation could actually be millions less.
For example, there could be a protocol change in the cryptocurrency's blockchain to allow for more than 21 million bitcoin in existence. Remember, Bitcoin is an open source cryptocurrency and can be changed to create hard or soft forks that create new cryptocurrencies or alter its functioning. Some examples of the former are bitcoin cash (BCHUSD), litecoin (LTCUSD), and dogecoin (DOGEUSD), which have made minor modifications to Bitcoin's source code and created new coins that have racked up billions of dollars in market valuations.
Effect on Bitcoin Miners
Block rewards and transaction fees are the most important sources of revenue for miners—the former more so than the latter in the current setup. High prices for bitcoin enable miners to cover operational costs and sustain business profits because they can sell their rewards stash in cryptocurrency markets.
When Bitcoin is close to reaching its limit, the reward amounts may not be enough to cover operational costs at miners, let alone generate profits. If and when the supply limit is reached, Bitcoin rewards are supposed to vanish.
In both instances, transaction fees are expected to pick up the slack. The amount of and mechanism for these fees depends on the state of Bitcoin's network at that point in time—i.e., whether it is being used as a medium of exchange or as a store of value. The former may incur reasonable fees to enable Bitcoin's use in daily transactions, while the latter scenario will have miners conducting fewer and more expensive transactions.
Another possibility being put forward is that of miners forming cartels amongst themselves. They might control supply to set high transaction fees or a fee amount that guarantees them a minimum in profits. Selfish mining is another possibility. In this form of mining, miners collude amongst themselves to hide new blocks and release orphan blocks that are not confirmed by Bitcoin's network. This practice will delay production of the final block in Bitcoin's network and ensure high rewards for the new blocks when they are finally released into the network.
The formation of a Bitcoin miners' cartel is not a far-reaching conclusion. Such groupings already exist in other commodities whose supply is constrained or controlled. For example, oil prices are influenced to a large degree by OPEC's production output. Prices in the diamond industry are also reportedly set by a cartel led by mining giant DeBeers.
Effect on Bitcoin's Network
The most valuable and useful aspect of Bitcoin is its network. Distributed ledger technology is a technological solution to the time-consuming bookkeeping and accounting that characterizes most financial transactions today.
If Bitcoin becomes popular as a medium of exchange in the future, its transaction numbers will surge. Past precedent has shown that there is a significant chance that the network will slow down. This is because Bitcoin's architecture, which relies on a distributed database to hold copies of massive ledgers, sacrifices speed for accuracy and integrity.
In such a scenario, it is likely that Layer 2 technologies, like the Lightning Network, will become responsible for confirming a majority of transactions on its network. Therefore, the cryptocurrency's actual network itself will be used only to settle large batches of transactions.
A second possibility is that the number of transactions on Bitcoin's network falls. Such a situation is possible when Bitcoin becomes a reserve asset. Trades involving the cryptocurrency will be few. Retail traders and small trading firms, who dominate its current trading ecosystem, will be eliminated and replaced by large institutional players and established trading firms. They will conduct fewer and more expensive trades that will incur high transaction fees from miners.
Effect on Bitcoin the Cryptocurrency
Bitcoin's inventor Satoshi Nakamoto designed the cryptocurrency to function as a medium of exchange for daily transactions. But its network has high transaction fees and slow processing times. Meanwhile, its scarcity and rising prices have become a magnet for speculative investors. Their bets on the cryptocurrency roulette have led to volatile price swings in the asset class deterring serious investors away from it. Regulators have criticized its ecosystem as a Wild West.
By the time that the last bitcoin is mined (or close to being mined), Bitcoin may have a more defined identity that it does currently. Side channels, like the Lightning Network, may have increased its network's transaction processing speed and enabled its use as a medium of exchange. Some countries like El Salvador are betting on such an eventuality and have made the cryptocurrency legal tender.
El Salvador made Bitcoin legal tender on June 9, 2021. It is the first country to do so. The cryptocurrency can be used for any transaction where the business can accept it. The U.S. dollar continues to be El Salvador's primary currency.
In the United States, the latest significant events are the Office of the Comptroller of the Currency (OCC) letter in January 2021 authorizing the use of crypto as a method of payment, PayPal Holdings, Inc.'s (PYPL) introduction of Bitcoin, and Tesla, Inc.'s (TSLA) acceptance of Bitcoin to purchase Tesla cars and solar roofs. Tesla reversed course on accepting Bitcoin in May 2021, citing environmental concerns around the resources required for Bitcoin mining.
The increasing scarcity in its numbers will also have driven up bitcoin's price and the corresponding valuation of cryptocurrency markets. Regulators tend to move quickly when increasing amounts of capital flows into an asset class, and it is likely that crypto markets and Bitcoin will also have come under the regulatory umbrella. That will be a sign for institutional investors to move into the cryptocurrency's ecosystem and stabilize its price swings with massive liquidity.
The Bottom Line
Bitcoin's 21 million supply cap is meant to control inflation that might, otherwise, result from an unlimited supply. But it has inflated the cryptocurrency's prices by making it a scarce commodity.
When Bitcoin reaches the supply cap, it is likely that miners will shift from block rewards to transaction fees as their main source of revenue. Development of side channels, like the Lightning Network, may result in Bitcoin's blockchain restricting itself to confirmation of large batches of transactions or ones that involve movement of significant numbers of bitcoins from one address on its blockchain to another. Bitcoin's identity—as a store of value and a medium of exchange—will also be more clearly defined than it is currently.
But none of these predictions are set in stone. The kinetic pace of developments in Bitcoin's ecosystem means that it is difficult to accurately predict its future. For example, the cryptocurrency's protocol may be changed to accommodate the production of more than 21 million bitcoins. Or, it may fall just shy of reaching 21 million.
Frequently Asked Questions
- What is Bitcoin's total supply?
The total supply of bitcoins is capped at 21 million.
- What will happen to miner fees when Bitcoin's supply limit is reached?
When Bitcoin supply reaches 21 million, miners will rely on transaction fees rather than block rewards, which will have vanished by then, for revenue.
- What will happen to Bitcoin's network when it reaches the supply limit?
When Bitcoin reaches the 21 million supply limit, it is likely that side channels, like the Lightning Network, will do most of the heavy lifting in confirming its transactions. The cryptocurrency's blockchain be responsible for confirming only very large batches of transactions or ones that involve movement of large sums of bitcoin from one address to another.
- What happens if Bitcoin supply fails to reach the 21 million cap?
One consequence of Bitcoin not reaching its planned cap is that it leaves open the possibility that the cryptocurrency's network will remain functional for a long time after 2140. In keeping with Bitcoin's economics, rewards for confirming these blocks will be minimal.