1. In a computing device, a method of generating a subgraph of key entities in a network, comprising: (a) executing at least one computer program on one or more processors to determine at least two types of network centrality metrics for a plurality of entities in a giant component of the network; (b) assigning rank-based scores to each network centrality metric value of each entity; (c) selecting some of the entities to form a tentative subgraph of key entities based on comparisons of the rank-based scores to preset cut-off criteria; (d) calculating the reach of the entities in the tentative subgraph of key entities and comparing that reach to a reach range; (e) if the reach falls within the reach range, assigning the entities in the tentative subgraph of key entities to a subgraph of key entities; and (f) if the reach does not fall within the reach range, iteratively repeating (c)-(e) using alternate rank-based scores cut-off criteria until a subgraph of key entities with a reach within the reach range is formed.