Small “villages” inside big cities

A very interesting study was conducted by a group from the USA, Germany, Great Britain and France. Scientists wondered how the number of social contacts between people and the size of the city where they live is related. And also: what is the probability that your contacts in the phone book know each other?

According to the results of the study several results were obtained. Focus on the two most non-trivial.
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First, with the increase in the size of the city, the number of social contacts in society is growing in superlinear dependence.

This means that when the settlement is increased N times the number of contacts between people increases more than N times (specifically, the coefficient is 1.12). Hereinafter, "contacts" refers to telephone calls, since the study was conducted on the basis of billions of anonymous logs from cellular networks in Portugal and the UK.


Dependence of the number of contacts on the size of the city, comparison of linear and superlinear dependence

People in big cities talk on the phone more often and with more people than residents of small towns. For example, a resident of a small Portuguese town for 15 months talking on a mobile phone, on average, with 5 subscribers. A resident of the capital Lisbon (565 thousand inhabitants) - an average of 11 subscribers. Accordingly, the latter also has more number of calls.

Nevertheless, if you take any two contacts of any subscriber, then the probability of mutual acquaintance of these people practically does not depend on the size of the city - and it’s “magic” 25%!


The coefficient of clustering, depending on the size of the city

This means that even in large metropolitan areas it is common for people to create relatively close communities (peculiar small “villages”) for communication with each other. Yes, here the clusters are larger, but the clustering coefficient is unchanged: 0.25.

Scientists suggest that between these two situations, however, there is an important difference. In small towns, clustering is, in many respects, forced. That is, people unite according to the principle of living nearby, studying together, etc. At the same time, in large cities a person can choose a cluster on other grounds, more freely and reasonably. For example, on professional interests or joint hobbies.