Full Idea
Sociological research has shown that the maximum 'natural' size of a group bound by gossip is about 150 individuals.
Gist of Idea
If a group is bound by gossip, the natural size is 150 people
Source
Yuval Noah Harari (Sapiens: brief history of humankind [2014], 02 'Legend')
Book Reference
Harari,Yuval Noah: 'Sapiens: a brief history of Humankind' [Vintage 2014], p.29
A Reaction
On the other hand, most of us can learn the names of a group of about 450. Maybe the 'known' group and the 'gossip' group are equally significant. Not much use for a modern state, but of interest to communitarians.