Bitcoin miners: Exploring a covert community in the Bitcoin ecosystem

In the Bitcoin ecosystem, bitcoin miners play an indispensable role in maintaining the Bitcoin’s blockchain. As a consequence, they are also rewarded with newly-created bitcoins and transaction fees. However, there are very limited studies to fully understand the characteristics and behaviors of bitcoin miners. In this paper, we conduct a comprehensive measurement study to shed insights into the community of bitcoin miners. By analyzing over ten-year bitcoin transaction logs, we observe that the scale of bitcoin miners shrinks significantly in recent years, and a small fraction of miners received most of newly generated bitcoins. In the early stage of the Bitcoin ecosystem, the mining reward was evenly distributed among miners, but later became more concentrated to a few highly active miners. For most of miners, their active duration is less than one year, and the interval between consecutive mining actions is more than 100 days. By further examining the transaction flows, we find that a significant portion of bitcoins have been hoarded for over 5 years, and the hoarding phenomenon becomes intense in recent years. We also discuss the implications of our findings, and believe our measurements enable us to have a better understanding of the whole Bitcoin ecosystem.