Understanding friendships, your own included

It is one of the strongest regularities in social graphs. It explains why networks close in on themselves without anyone deciding so.

Formulated in 1954, it holds that mixing between groups reduces prejudice. The conditions it sets are more demanding than its uptake suggests.

Changing city does not erase relationships, it changes their nature. Longitudinal surveys show faster than average replacement.

Neighbour relationships have receded in personal networks since the 1960s. That retreat mainly concerns one precise kind of use.

It is not only the number of relationships that differs, it is their reach. A 2022 analysis of massive data put figures on what surveys had suggested.

Whether they replace or complement offline relationships was asked as early as the 1990s. The answers have changed twice.

Depending on the method used, the answer runs from three to several thousand. Those figures do not contradict each other: they measure different relationships.

The 1967 experiment is famous; its completion rate less so. Large-scale replications confirmed the order of magnitude without lifting the main objection.

Our relationships resemble us, one of the most consistent findings in network sociology. Inferring a preference for the similar is a frequent error.

A 1973 article argued that distant acquaintances are more useful than close friends for finding a job. A 2022 experiment tested it on twenty million people.

One hundred and fifty stable relationships: the figure has circulated everywhere since the 1990s. Its origin is a regression line drawn on primates.