Core–periphery structure

[clarification needed] Borgatti & Everett (1999) suggest that, in order to overcome this problem, each node be assigned a measure of ‘coreness’ that will determine its class.

Identifying core–periphery structures can help circumvent this problem by categorizing hubs as part of the network's core (Rombach et al., 2014, p. 160).

It is possible to find that a set of highly central nodes in a graph does not make an internally cohesive subgraph (Borgatti & Everett, 2000)...

The concept was first introduced into economics as "centre-periphery" by Raúl Prebisch in the 1950s, but the origin of the idea could ultimately be traced back to Thünen's Isolated State (1826).

[1] However, the qualitative notion that social networks can have a core–periphery structure has a long history in disciplines such as sociology, international relations (Nemeth & Smith, 1985), and economics (Snyder & Kick, 1979).

Network with an idealized core–periphery structure
In this idealized matrix, the blue block represents core-core links, the white block represents the absence of periphery links and the red quadrants represent core–periphery ties.