Dynamic Social Network Modeling and Analysis Workshop Summary and Papers (2003) / Chapter Skim
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Identifying International Networks: Latent Spaces and Imputation
Identifying International Networks: Latent Spaces and Imputation
Pages 345-360
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Hoffi Corey Lowell Lofdahl Political Science Statistics Simulation & Information University of Washington University of Washington Technology Operations Seattle, Washington Seattle, Washington SAIC 98195 98195 Burlington, MA 01803 Introduction Most analyses of world politics and studies of national security policies recognize the interdependence among the salient actors across the salient issues. ~aditionallv.
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developed probabilistic models of links among actors based on latent positions of actors in an unobserved "social space." We apply such a model a large database on international relations that is typical for the national security and international politics literatures, and discuss making predictive inference on links that are missing at random. In particular, we analyze the interactions among important social actors in Central Asia, using data taken from the Kansas Event Data Survey an autos mated textually oriented data generating process (Schrodt, Davis and Weddle 1994; Gerner, Schrodt, Francisco and Weddle 1994)
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Typically a news summary is used, ideally one that is already available in a machine readable format. The two current de facto publically available standards are the Reuters news service lead paragraphs or the Foreign Broadcast Information Service (FBIS)
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AH BY Talks on defusing an explosive cri TWEEN IRAQ AND KUWAIT COG sis in the Gulf collapsed Wednesday LAPSE when Kuwait refused to give in to Iraqi demands for money and territory, a Kuwaiti official said. August 2,1990 IRAQ INVADES KUWAIT, OIL Iraq invaded Kuwait, ousted its lead PRICES SOAR AS WAR HITS ers and set up a pro-Baghdad go~rern PERSIAN GULF ment Thursday in a lightning pre-dawn strike that sent oil prices soaring and world leaders scrambling to douse the flanks of war in the strategic Persian Gulf.
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For example while Iraq's invasion of Kuwait by itself generates only a single event with WElS code 223-military force-the invasion triggers an avalanche of additional activity throughout the international system as states and international organizations denounce, approve or comment, so the crisis is very prominent in the event record. This kind of implicit triggering is analyzed and described in Throat and Mintz (1988)
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We turn to the application of latent space analysis of social networks using these ciata in the following sections. Latent Space Models of Network Structures Let pi j denote the value of a relationship between agent i and agent j; these relationships may be measured discretely or continuously.
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to estimate several of the classic social network analysis data sets.7 The basic setup is quite general and can be even more widely employed. Estimation of Network :Links in CASIA database We use this framework to estimate the network structure of the political interactions of the primary actors in Central Asian politics over the period from 1989 through 1999.
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Equation 3 was estimated using direct optimization of the maximum likelihood to generate starting values for the MCMC. One million iterations of the chain were run to obtain estimates of the parameters or and ,5 as well as the latent positions Z and their underlying variance ~2 The negative coefficient for the distance covariate indicates a lower probability of interaction at greater distances, consistent with many published results from different contexts.
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However, practically, it may be useful to use imputation methods along with the latent space estimates to gauge whether or not a link that does not turn up actually may be missing at random. We conduct an experiment using the CASIA database through the following procedure: I
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Compare these results to a standard, logistic framework with the same covariates. The results of this experiment are quite supportive of using latent space to predict non-sampled or hidden network linkages.
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The upshot of this experiment is the important implication that if we sample network ties at random, then estimate the latent positions, this approach can be used to predict the Yi,j that were not sampled. Although quantitative models in international relations that make actual predictions are themselves rare (SchroUt 2000; King and Zeng 2001; Ward and Gleditsch 2002)
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: A New Event Data Framework for a Post Cold War World. Annual Meetings of the American Political Science Association Boston, MA: .
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2002 in press. "Latent Space Approaches to Social Network Analysis." Journal of the American Statistical Association tbattba)
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Annual Meetings of the American Political Science Association Boston, MA: SchroUt, Philip A and Alex Mintz.
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