Bargaining Power on the Supreme Court

Abstract

How can we figure out relative bargaining power within the Supreme Court? We argue that fluidity, the switching of votes by a justice between the initial internal conference vote and the final reported vote in a case, can reveal the likely location of the majority opinion - because all else equal justices should be less likely to switch the happier they are with the majority opinion. Different theories make various predictions for opinion location. We draw out the implications for how happy a particular choice of assignee should make each justice in the majority. This in turn should correlate to the probability of vote switching. We then compare the predictions of each model to observed vote switching. We make use of multilevel probit regression and roughly 40 years of Supreme Court vote data. Among the theories we consider, we find that the evidence from fluidity supports the conclusion that authorship does matter. In particular, the evidence is compatible with the bargaining and opinion assignment model in Lax and Cameron (2007), suggesting that power within the Court does lie partially in the hands of opinion authors and thus of the Chief Justices who pick them, as constrained by the need to maintain a majority coalition.