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WORKING PAPER
Tau-b or Not Tau-b: Measuring Alliance Portfolio Similarity
Ritter, Jeffery M.Signorino, Curtis S. Abstract The pattern of alliance commitments among states is commonly assumed to reflect the extent to which states have common or conflicting security interests. For the past twenty years, Kendall's tau-b has been used to measure the similarity between two nations' ``portfolios'' of alliance commitments. Widely employed indicators of systemic polarity, state utility, and state risk propensity all rely upon tau-b. We demonstrate that tau-b is inappropriate for measuring the similarity of states' alliance commitments. We develop an alternative measure of alliance portfolio similiarity, S, which avoids many of the problems associated with tau-b, and we use data on alliances among European states to compare the effects of S versus tau-b in measures of utility and risk propensity. Finally, we identify several problems with inferring state interest from alliance commitments and we provide a method to overcome those problems using S in combination with data on alliances, trade, UN votes, diplomatic missions, and other types of state interaction. Keywords alliances ordinal risk similarity tau-b utility File
Uploaded 04-02-1997 Document ID Number 448 |
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