The LESSON LEARNT FROM Borgatti, S. 1995. Centrality and AIDS

"Centrality measures are commonly described as indices of prestige, prominence, importance, and power - the four Ps." There are usually four measures, which were developed by Freeman (1979) and Bonacich (1972), being used in network analysis: degree, closeness, betweenness, and eigenvector centrality. "Degree centrality may be defined as the number of ties that a given node has." When all else is equal, we could describe degree centrality as measuring the risk (or opportunity) of receiving whatever is flowing through the network. Furthermore, in eigenvector centrality, it was demonstrated that "it wasn't just how many people a person knew that counted, but how many people the people that they knew knew." That's to say, an actor that is connected to many actors who are themselves well-connected is assigned a high score, but an actor who is connected only to near isolates is not. "Closeness centrality may be defined as the total graph-theoretic distance of a given node from all other nodes." "Betweenness centrality is defined as the number of times that a node needs a given node to reach another node." Thus, also according to Granovetter's (1973) definition, actors with many weak ties are more important than others because removing those actors would do the most damage to transmission possibilities throughout the network.