Table 1

Measures and key characterises used in social network analysis20 21 23 24

Global structure: measureCharacteristic
Network structural analysis
CohesionDescribes the interconnectedness of actors in a network. There are three types of measures of cohesion:
 DistanceDistance measures the number of ties that separate two actors. If two nodes are directly connected, the distance is one. If these two nodes are separated by one node, the distance is two, and so on.
 ReachabilityReachability defines the degree by which a node can be reached by other nodes. If a certain number are unreachable by some actors, it means that the network is fragmented. Reachability corresponds to the number of steps maximally needed to reach from one node to any other node in the network.
 DensityDensity is defined as the number of existing ties divided by the number of possible ties. Dense networks are thought to be good for coordination of an activity among actors. However, the downside to having dense networks is that they can entrench a particular value system and norm.
CentralityThe degree of centrality represents the number of ties an actor has. If an actor has many ties compared with other actors, this indicates that this actor has a central position in the network. Centrality can also characterise the shape of a whole network. To analyse centrality further, there are three measures:
 Degree centralityIs the sum of all other actors who are directly to a particular actor. It signifies activity or popularity.
 Degree closenessIs based on the notion of distance. If an actor is close to all others in the network (a distance of no more than one), then that actor is not dependent on any other actor to reach everyone in the network.
 Betweenness centralityIs the number of times an actor connects pairs of other actors, who otherwise would not be able to reach one another, and is an indicator of the power that actor has in the network.
Within structure: measureNetwork pairwise (between-actor) analysis.
Tie strengthRelates to the intensity of the connection between two actors.
EmbeddednessIs the extent to which network members share common peers, reflecting the number of neighbours that two connected members have in common.
Role and position: measure Characteristic
Network relational analysis
Structural equivalenceActors that have exactly the same ties to exactly the same others in a network.
Regular equivalenceLess formal than structural equivalence. Actors who are defined as being regularly equivalent have identical ties, but not necessarily to identical others.
Automorphic equivalenceAutomorphic equivalence asks if the whole network can be re-arranged, putting different actors at different nodes, but leaving the relational structure or skeleton of the network intact.