Dynamic Social Network Modeling and Analysis Workshop Summary and Papers (2003) / Chapter Skim
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Balancing Efficiency and Vulnerability in Social Networks
Balancing Efficiency and Vulnerability in Social Networks
Pages 253-264
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From page 253... ...
By introducing two concepts, network efficiency and vulnerability, we show that efficiency is compromised more in networks characterized by high degree centralization when degree and betweenness centrality are not distinct than in other networks, following the removal of network positions. Vulnerability is the loss in efficiency resulting from the elimination of nodes.
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From page 254... ...
showed that in exchange networks, where the value of the commodity exchanged is lost to the person who relinquishes it, centrality measures do not predict who will have power to control resources. As an alternative to traditional centrality measures, this study (Cook, 1983)
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This models the likely effect of the removal of a node in a social network. When this more stringent type of vulnerability is considered the rewired lattice and rewired bipartite networks do well.
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The reduction in efficiency resulting from random attacks, attacks aimed against individuals with high betweenness centrality and attacks aimed against individuals with high degree were was calculated for each network. Table ~ summarizes the measures calculated for each network and compared in the analysis that follows.
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To ensure networks were connected each of the eighty vertices in the larger class was randomly connected to one of the vertices in the smaller class and 120 additional randomly chosen edges were then added. Results Node Vulnerability A comparison of the loss in efficiency for the random, scale free, rewired bipartite and rewired lattice structures to removal one node from the network, for five consecutive attacks confirm results of prior research that scale free networks are better than random networks at resisting random attacks, but they do not do better then a rewired bipartite graph structure.
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. ' -'-''-'-'''''''''1 -- -"'''''' '''-''''' -- -'-''1 -- '- ' I Random Betweenness Degree Attack Type Average Efficiency during 5 Attacks Cnteria for Tareet Selection .
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As average degree increases network efficiency decreases. This is not only because more people are removed from the network, but also because there is an increasing likelihood that a random person will be connected to a person with higher degree centradity The implication is that cells of criminal activity, connected by a few individuals with high betweenness are very vulnerable to the discovery of these individuals.
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Table 4. Initial efficiency, betweenness centralization and degree centralization with standard errors for six network structures.
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Scale-free networks are the least resistant of all networks to strategic attacks. Adding random connections to the lattice and bipartite networks increases efficiency without sacnf~cing resilience.
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Attack 4 Attack ~ '-i:.; Randon, ~—Scale Free Bipartite ~Elipartite-R -Latticed _ Latt~ce2R,' Figure 3. Loss of Efficiency resulting from 5 random hits.
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The focus of this paper was on the resistance of networks to random attacks and attacks aimed at positions of high centrality. Future work wild expand this to test network resilience to attacks based on other cnteria.
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1983. "The Distribution of Power in Exchange Networks: Theory and Expenmenta1 Results." American Journal of Sociology 89:275-305.
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