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The Genealogy of Law

Published online by Cambridge University Press:  04 January 2017

Tom S. Clark*
Department of Political Science, Emory University, 327 Tarbutton Hall, 1555 Dickey Drive, Atlanta, GA 30322
Benjamin E. Lauderdale
Methodology Institute, London School of Economics, Columbia House, Houghton Street, London, WC2A 2AE, UK. e-mail:
e-mail: (corresponding author)
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Many theories of judicial politics have at their core the concepts of legal significance, doctrinal development and evolution, and the dynamics of precedent. Despite rigorous theoretical conceptualization, these concepts remain empirically elusive. We propose the use of a genealogical model (or “family tree”) to describe the Court's construction of precedent over time. We describe statistical assumptions that allow us to estimate this kind of structure using an original data set of citation counts between Supreme Court majority opinions. The genealogical model of doctrinal development provides a parsimonious description of the dependencies between opinions, while generating measures of legal significance and other related quantities. We employ these measures to evaluate the robustness of a recent finding concerning the relationship between ideological homogeneity within majority coalitions and the legal impact of Court decisions.

Research Article
Copyright © The Author 2012. Published by Oxford University Press on behalf of the Society for Political Methodology 


Authors' note: We thank Brandon Bartels, Barry Friedman, John Kastellec, Drew Linzer, and Jeff Staton for helpful comments and suggestions. We also thank Josh Strayhorn for helpful research assistance. This research was supported by the National Science Foundation (SES-0961058).


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