Wow. Our experiment is off to a great start—let's see if we can finish it off sooner than expected.
The diagram below comes from The Upshot, and it shows how much various Supreme Court justices agree with each other:
In general, there are no surprises. You can rank the justices on a scale from most liberal to most conservative, and there's more agreement the closer they are ideologically. But here's one thing that might surprise you: The lowest level of agreement, between Ruth Bader Ginsburg and Clarence Thomas, is 65 percent. That is, the two justices who are the most extreme polar opposites still agree with each other two-thirds of the time.
This tells you a lot about what the Supreme Court actually does most of the time: it rules on obscure tax cases and agency regulation cases that don't always break down on the usual left-right spectrum. When it comes to high-profile cases, you get a lot of 5-4 decisions. But on the majority of less celebrated cases, when the political spotlight is turned off, there's a surprising amount of consensus on what the law means.