Core-Periphery Structure

A core-periphery structure is a type of network structure in which core actors are densely interconnected, whereas periphery actors are sparsely interconnected and only connected to core actors. An ideal core-periphery structure consists of a core where actors are all linked with each other and a periphery where actors are only linked to those in the core but no one in the periphery. While the ideal core-periphery structure is very rare in practice, many social networks, as well as other complex networks, resemble a core-periphery structure to varying degrees, with a densely interconnected core surrounded by a sparse periphery. This entry discusses key features of the core-periphery structure, introduces popular methods for detecting such structures, and presents some examples.

The defining feature of a core-periphery structure is a partition of a network into two sets, a well-connected core and a sparsely connected periphery. There has been no consensus about the exact extent of the connections between the core and the periphery, however. Some scholars suggest a core actor should be connected to all periphery actors, while others contend that it only needs to be connected to some periphery actors. The common ground is that core actors are expected to be reasonably well connected to periphery actors.

Usually only a relatively small number of actors are located in the core, but they play a prominent role in the overall network. Compared with periphery actors, they possess more power and enjoy more prestige due to their structural advantage. They are also more instrumental in diffusing information, innovations, and social norms. Dependency may emerge as periphery actors become dependent on the core for key resources embedded in the network.