Supreme Court Ideology Project

Trend Lines

The graphs below displays the updated probability, after each new vote, of the most recently appointed justices being either the most extreme justice on the court or more extreme than the justices they replaced.

At each iteration, we learn more about Justices Roberts and Alito relative to the other justices. The solid trend lines plot the probability at each round that a given justice is the most conservative. The dotted lines represent the probability that the justice is more conservative than was Justice O’Connor. The dashed lines represent the probability that the justice is more conservative than was Chief Justice Rehnquist.

As one might expect, Justice Alito’s position does not change noticeably during the earlier votes because he was not casting votes at that time. His position does change slightly as our beliefs about the other justices change.

The next graph displays analogous information for Justices Sotomayor and Kagan. The solid trend lines plot the probability at each round that a given justice is the most liberal sitting justice. The dotted lines represent the probability that a justice is more liberal than was Justice Souter, whom Justice Sotomayor replaced. The dashed lines represent the probability that a justice is more liberal than was Justice Kagan replaced. As with Justice Alito in the previous graph, little change until Justices Sotomayor and Kagan begin casting votes.