URL: https://arewedecentralizedyet.online/
This page measures the concentration of user data on the Fediverse, the Atmosphere, and public git forges according to the Herfindahl–Hirschman Index (HHI) and the Shannon Index.
HHI is an indicator from economics used to measure competition between firms in an industry. Mathematically, HHI is the sum of the squares of market shares of all servers. Values close to zero indicate perfectly competitive markets (eg. many servers, with users spread evenly), while values close to 10000 indicate highly concentrated monopolies (eg. most users on a single server). In economics, values below 100 are considered "Highly Competitive", below 1500 is "Unconcentrated", and above 2500 is considered "Highly Concentrated".
The Shannon Index is an entropy-based measure used in ecological studies. It is computed the same as Shannon entropy using the natural log: the negative sum over all servers of the "market share" times the log of the market share. Lower values indicate lower entropy (a high concentration of one species), while higher values indicate a more even population. In this context, the maximum value is the number of servers, which would mean that all servers have equal population.