Definition. Herfindahl Index, originally a measure of competition, is adapted here as a metric for decentralization. It is defined as the sum of squared address shares of current supply across the network. Gini Coefficient and Percent of Supply Held by Top 1% Addresses are related concentration metrics.

Technical. For ETH and ETH tokens, exchange addresses, smart-contract addresses, and other special asset-specific addresses (e.g. team-fund addresses) are excluded. For ETH tokens, burn addresses are excluded.

Interpretation. A large score indicates high concentration of supply, a small score indicates more evenly distributed funds across addresses.