[PeterisP]

Meh, since there's no hard registry of identities of owners, if someone would make and popularize an inequality index, that index would simply be gamed (e.g. by artificial splitting of accounts) to show whatever is most beneficial to show, as soon as a gameable metric is used for a practical purpose (e.g. making better investment choices), it ceases to be useful for that purpose as it gets manipulated, see Goodhart's law https://en.wikipedia.org/wiki/Goodhart%27s_law .