Skip to main content

Statistical Mechanics of the US Supreme Court

Author(s): Lee, Edward D; Broedersz, Chase P; Bialek, William

To refer to this page use:
Abstract: We build simple models for the distribution of voting patterns in a group, using the Supreme Court of the United States as an example. The maximum entropy model consistent with the observed pairwise correlations among justices’ votes, an Ising spin glass, agrees quantitatively with the data. While all correlations (perhaps surprisingly) are positive, the effective pairwise interactions in the spin glass model have both signs, recovering the intuition that ideologically opposite justices negatively influence each another. Despite the competing interactions, a strong tendency toward unanimity emerges from the model, organizing the voting patterns in a relatively simple “energy landscape.” Besides unanimity, other energy minima in this landscape, or maxima in probability, correspond to prototypical voting states, such as the ideological split or a tightly correlated, conservative core. The model correctly predicts the correlation of justices with the majority and gives us a measure of their influence on the majority decision. These results suggest that simple models, grounded in statistical physics, can capture essential features of collective decision making quantitatively, even in a complex political context.
Publication Date: Jul-2015
Electronic Publication Date: 10-Apr-2015
Citation: Lee, Edward D, Broedersz, Chase P, Bialek, William. (2015). Statistical Mechanics of the US Supreme Court. JOURNAL OF STATISTICAL PHYSICS, 160 (275 - 301. doi:10.1007/s10955-015-1253-6
DOI: doi:10.1007/s10955-015-1253-6
ISSN: 0022-4715
EISSN: 1572-9613
Pages: 275 - 301
Type of Material: Journal Article
Version: Author's manuscript

Items in OAR@Princeton are protected by copyright, with all rights reserved, unless otherwise indicated.