Mining is an intensive business and competition is fierce in the mining industry. It takes large, expensive equipment to mine and a lot of electrical energy to power them. We do not know which of the one-time numbers (data) will work, so the goal is to eliminate them as quickly as possible and switch to another one. In the early days of mining, miners realized that they were able to increase their chances of success by combining in mining pools, that is, by sharing their computing power (and sharing the rewards among themselves). Even when the aforementioned rewards were shared by multiple miners, there were still plenty of incentives to keep track of the rewards (or to persuade miners to follow the rewards). Every time a new block is mined; the successful miner receives a bunch of newly created bitcoins. At first this group consisted of 50 bitcoins, but then dropped to half, or 25. 12.5, corresponding to 119,000 USD as of October 19, and 6.25 today. The reward will continue to be halved every 210,000 blocks or approximately every four years until it reaches zero. At this point, 21 million bitcoins (when Bitcoin was launched, the total supply of this digital currency was planned to be 21 million.) all will be mined and the miners will only depend on fees to maintain the network. Many people worry that miners do pool organizations. Because if the power of a pool network exceeds 50% of the total mining power, its members can potentially spend bitcoin, reverse transactions, and spend it again. They can also block other people's transactions. Simply put, this miner pool can have the power to overcome the disorganized nature of the system by validating fraudulent transactions thanks to its majority power. The scenario we described above could bring Bitcoin to an end, but even the so-called 51% attack probably won't cause bad actors to reverse old transactions because the Proof of Work makes this process very labor intensive. In order for a pool to return and change the blockchain, it needs to control such a large part of the network that it would probably be a pointless attempt to achieve its purpose. Another point of view brings the following question into minds: "When you control the entire currency, who will be left behind to trade that currency?" From the miners' point of view, a 51% attack is materially a suicidal proposition. Ghash.io, a mining pool, promised that when it reached 51% of the network's computing power in 2014, it would not voluntarily exceed 39.99% of the rate of Bitcoin provisioning to maintain confidence in Bitcoin's value. Still, other actors such as governments may find the idea of such an attack interesting. However, again, the size of Bitcoin's network will make it extremely expensive even for an individual government as well as for a group of governments against digital currencies. Another concern with miners is the tendency of miners to operate heavily in parts of the world where electricity is cheap, such as China (or Quebec, following Chinese crackdown in early 2018).