Supreme Court voting patterns show high predictability

Supreme Court rulings can dramatically shape American policies, but the Court's decisions may actually be quite predictable, according to a new study published in the Nov. 9 issue of the online journal PLoS ONE.

The researchers, led by Roger Guimerà and Marta Sales-Pardo, created a computational model to investigate whether it would be possible to predict a justice's vote based on the other justice's votes in the same case. They found that their method, which relied on previous work developed to uncover hidden associations in complex social networks, was more accurate at predicting justice's votes than were forecasts made by legal experts or algorithms that take the content of the cases into account. These results are definitely "something to keep in mind when discussing how legal decisions are made", say the authors.

They also found that predictability decreased during the 50-year period spanning from the Warren Court to the Rehnquist Court, and that court predictability has been significantly lower during Democratic presidencies than Republican, but the meaning of these results remains unresolved.