Betweenness Centrality in Social Network Analysis

Social Network Analysis (SNA) is a method used to study relationships and interactions among entities in various types of networks such as social, organizational, or technological. One of the key concepts in this analysis is betweenness centrality, which identifies nodes acting as crucial intermediaries in the flow of information.

Definition of Betweenness Centrality

Betweenness centrality of a node is the ratio of the number of shortest paths between any two other nodes that pass through this node to the total number of shortest paths between those nodes. In other words, it measures how often a node serves as an intermediary in communication between other nodes.

Importance of the Betweenness Measure

This metric highlights nodes that are critical for communication and information flow within the network. Nodes with high betweenness have strategic significance—they control many communication paths and influence the speed and efficiency of information transfer.

Furthermore, nodes with high betweenness can be critical points whose removal results in the network losing cohesion, meaning communication between remaining nodes becomes difficult or impossible.

Betweenness in Star Networks

A star network topology consists of one central node connected directly to all others, which are not interconnected. In such a network:

• The central node has maximum betweenness because all shortest paths connecting any two other nodes pass through it.
• All other nodes have zero betweenness as they are not “between” any other nodes.

The network’s betweenness centralization is maximal, indicating the central node’s absolute importance for network cohesion.

Consequences of Removing the Central Node in a Star Network

Removing the central node completely breaks the network — all connections are lost, and peripheral nodes lose the ability to communicate with each other. The network loses cohesion, meaning information can no longer flow freely.

Figure 1. Removing the central node in a star network

Interpretation and Application in Social Network Analysis

Betweenness centrality helps understand which individuals serve as “bridges” in a network and the consequences of their loss. In practice:

• It identifies key employees or informal leaders in organizations,
• Detects potential failure points in communication networks,
• Supports viral marketing strategies by selecting individuals best suited to spread information,
• Provides insights into social dynamics and information flow within groups.

Summary

Betweenness centrality shows how often a node acts as a bridge in a network. Nodes with high betweenness are key for communication and connecting different parts of the network. Their removal can disrupt information flow. This measure helps identify important individuals and potential weak points in social or organizational structures.