In “Quantifying Decentralization”, Balaji S. Srinivasan (the CTO of Coinbase) describes the Nakamoto coefficient - a method beyond the Gini coefficient in measuring how centeralized these networks really are.

https://news.earn.com/quantifying-decentralization-e39db233c...

"The basic idea is to:

(a) enumerate the essential subsystems of a decentralized system,

(b) determine how many entities one would need to be compromised to control each subsystem, and

(c) then use the minimum of these as a measure of the effective decentralization of the system.

The higher the value of this minimum Nakamoto coefficient, the more decentralized the system is."