What Is the Role of Mining Pools in Centralizing or Decentralizing the Hash Rate?

Mining pools are groups of miners who combine their hash power to increase their probability of finding a block and sharing the reward. While they decentralize the income among many individual miners, they can centralize the control of the hash rate into the hands of a few pool operators.

If a few large pools collectively control over 51% of the total network hash rate, it creates a vector for a potential 51% attack, even if the individual miners are geographically dispersed.