Three Basic Measurements
Degree is the simplest of the three measures: it counts the number of direct connections to and from an individual. Such direct ties can be divided into those leading to an individual--the count of these is referred to as in-degrees--and those leading away from an individual (the count called being out-degrees). An individual with a relatively high number of degrees can be described as a hub or connector. A high degree centrality is not always desirable: it is whom you are connected to that is important. However, a high in-degree does show that a person is particularly sought after or preferred in the network.
A person with just a few connections can still be a central employee if he ties together otherwise disconnected people. Betweenness is a measurement of how often a person is found on the shortest path between all possible pairings of people in the network. In other words, a person with high betweenness ties together groups.
This can be a very powerful position; as such individuals play the role of the middleman or broker in the organization. In the case where such a person is the only connection between, say, departments, he or she can cut off information between these departments. Therefore, in addition to a middleman role, he or she may have a gatekeeping role or bottleneck role too.
A manager might, rightfully, worry about what would happen if this person was to leave the organization, as the important, strategic connections sometimes are lost when a person with a high betweenness leaves the company.
As a betweenness score cannot be standardized (converted to a number between 0 and 1, for instance), the individual’s betweenness score has to be compared to the others’ in the network. A betweenness of 0 indicates that the person is not on any of the shortest paths in the network. A betweenness score of 0 is not necessarily a problem.
A final centrality measurement is closeness. Closeness describes how easy it is for the person to access the whole network. In other words, it describes how close the individual is to all others in the organization.
The number of steps it takes the individual to get connected with any other person in the network determines the person’s closeness. There is a step between every person that is connected and multiple steps for those that are tied together indirectly. A high closeness centrality means that there are few steps between the individual and the remaining network.
A person with a high closeness centrality is more in touch with the network than others and therefore more likely to know what is going on.