The security and viability of cryptocurrencies like Ethereum come from the decentralized nature of miners. Without large distributed networks of participants it would be easy for one entity or small group of entities to take control of the blockchain and control which transactions get added. We therefore investigated the distribution of miners on the Ethereum blockchain by taking a statistically representative sample of the blocks for each day, during the period 2015-07-31 to 2022-02-04. We found that from early on the majority of blocks were mined by mining pools, which are groups of people who come together to aggregate their compute power to improve their chances of mining blocks and bring some predictability to their rewards. However, we found that on average only 3 or less addresses make up more than 50% of the blocks minded for a month. We also analyzed in more detail the top 20 miners over the period and found interesting results there as well.

The video "Top 50% of blocks mined" displays the least number of miners who together mined 50% of blocks monthly. It is clear that except for the first month (2015-08), 2 to 4 miners (pools) domained over half the blocks. The "Top 20 miners" video plots the change of the top miners over the 6 years period. Unfortunately, such "proof of work" block chain system was highly centerlized.