What Is In-Degree Centrality in Network Analysis?
Discover how counting incoming connections to a node in a network reveals its influence, a core concept for identifying prestige and authority.
In network analysis, in-degree centrality is a measurement used to evaluate the prominence of a point within a network. It quantifies influence or importance by focusing on the connections directed toward a specific point, rather than the connections it sends out. This metric helps identify nodes that serve as significant receivers of information, attention, or resources. By counting these incoming links, analysts can pinpoint hubs of activity or prestige in various systems.
The Building Blocks of a Network
A network consists of two components: nodes and edges. Nodes are the individual points within the system, such as people in a social circle or websites on the internet. Edges represent the connections between these nodes, like friendships or hyperlinks. In an undirected network, relationships are reciprocal, while a directed network features one-way connections, such as on Twitter. In-degree centrality applies exclusively to these directed networks, as it depends on counting connections with an incoming direction.
Calculating and Interpreting In-Degree Centrality
A node’s in-degree centrality is the total number of edges that point toward it from other nodes in the network. For example, in a small network where influence is tracked, if an individual named Sarah receives influence arrows from three different people, her in-degree centrality score would be three. Another individual, Mark, who receives an arrow from only one person, would have an in-degree score of one. A high in-degree centrality score suggests that a node is a significant target of connections, which is interpreted as an indicator of popularity or authority. Conversely, a node with a low in-degree score is not a major recipient of attention from its peers.
Applications of In-Degree Centrality
In social media analysis, a user’s in-degree centrality is their follower count. An account on a platform like Instagram or X (formerly Twitter) with millions of followers has a very high in-degree score. This quantifies their status as a major influencer or public figure.
In the academic world, networks are formed by scholarly papers and their citations. When a new research paper cites an older one, it creates a directed edge from the new work to the cited work. A paper that has been cited by hundreds or thousands of other papers has a high in-degree centrality. This high score signals that the paper is foundational or highly impactful in its field.
The structure of the World Wide Web can also be analyzed using this measure. Websites are nodes, and hyperlinks are directed edges. A website with a high in-degree centrality has many other websites linking to it. Search engines may interpret these incoming links as endorsements of quality or authority. This concept is a component within algorithms like Google’s PageRank that determine a website’s ranking in search results.