Policy Voting: What Amici Tell Us About Law

Alexandra Dunworth, Daniel E. Ho & Joshua Fischman


We compile a new database of individual merits positions by over 600 of the most active amicus groups in over 14,000 briefs in Supreme Court cases from 1978-2006. Matched to individual votes by each justice, this rich data seamlessly addresses a host of previously difficult-to-answer questions about interest group litigation in the Court. We illustrate how amici shed insight into long-standing debates about law, policy, and judicial decisionmaking. Since interest groups are primarily policy-motivated, they provide one crucial comparison group to substantively understand "attitudinalism" and jurisprudential considerations on the Court. Our findings are twofold. First, if one is willing to assume a unidimensional policy space --- as most conventional approaches do --- then the vast majority of groups is entirely to the left or to the right of the Court. This stems from the fact that interest groups on average disagree with a unanimous Court in nearly one out of six cases. Second, we show that unidimensionality is violated across a host of issue areas, where interest group considerations deviate sharply from those of the Court. Our evidence demonstrates that the Court operates in a space that is significantly more confined or distinct than that of interest groups.

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