Text excerpt for “Conceptualizing resilient energy transitions: the case of energy regions” (Binder et al. 2016): connectivity As in other systems that are characterized by complex flows of materials, information or people, a sustainable energy system can be described by the two variables resilience and efficiency (Lietaer et al. 2011; Ulanowitz et al. 2009). The resilience of a given system can be broken down to the basic constituting properties of 1. “diversity”, and 2. “connectivity”. Diversity is dealt with in the prior section of this paper (referring to the diversity as the combination of the system-properties variety, balance and disparity, following Sterling 2007). Connectivity, on the other hand, can be measured by various different network metrics linked to basic network properties (see Boccaletti et al. 2006 for an overview). For social networks, three important metrics characterizing a network are (average) path-length (= node-to-node pathway steps), centrality (= number of connections per node) and modularity (= distribution of nodes and links throughout the network) (see Luthe et al. 2012; Wasserman & Faust 1994).