How many decisions of the Supreme Court end up in a tight spot between judges considered to be "progressive" and those considered to be "conservative"? I know that 5-4 decisions are rare in the first place, but how many of them hinge on party lines in the court?

  • 2
    Do you consider ~20% rare? brookings.edu/opinions/the-supreme-courts-divided-decisions
    – DJohnM
    Jun 28, 2018 at 7:24
  • 1
    @DJohnM I suspect most people today would be surprised at how low that figure is, yes. Virtually all of the "major" decisions are divided, and those are the ones we hear about the most, and often have the largest impact on people, giving off an impression that 5-4 decisions are frequent. Jun 28, 2018 at 8:49
  • 3
    Are you asking about split that happens to be between progressive and conservative judges, or a split that is caused by the fact that the judges are progressive and conservative? Presumably, at least some 5-4 decisions have little to do with political alignment causality wise.
    – user4012
    Jun 28, 2018 at 10:42
  • 1
    @user4012 I'm asking about splits that occur precisely between judges that are considered to be "progressive" and those considered to be "liberal" by the general public. I assume at least some splits don't happen precisely along party lines. Jun 28, 2018 at 14:15
  • 1
    I think the normal metric is "appointed by a R/D president" which is simpler to directly measure than a judge's personal bias.
    – user9389
    Jun 28, 2018 at 15:03

2 Answers 2


I manually recorded the votes on 2012 supreme court cases from the list on wikipedia. There's a page for each year since 2000 thats in the same format. You (or someone with some time on their hands here) could probably whip up a webscraping script to capture for each year.

For 2012, of the 20 5-4 split cases on the page, 14 were split along party lines with Kennedy swinging the vote. The remaining 6 cases were mixed. The supreme court took 79 cases in 2012, so cases split across ideological lines accounted for about 18% of cases in that year.

It is of course important to take into account that judicial philosophy doesn't completely correlate with political philosophy, which becomes more apparent when a justice strongly adheres to a judicial philosophy (as opposed to using a judicial philosophy to justify a politicized ruling). Several of those "mixed-party" votes were Scalia adhering to his Textualism which would lead to cases such as Maryland v. King, a fourth amendment case, in which Scalia was joined in his dissent by Ginsburg, Sotomayor, and Kagan.

  • 1
    I would suggest adding how many cases in total were seen in 2012 for completeness sake. This gives a better idea of the percentage of cases which may have been decided via party lines relative to cases heard. It's available in the link, but it's best for answers to have relevant information included without needing to follow links.
    – dsollen
    Jul 3, 2018 at 15:15

So I looked up SCOTUS Blog which documents statics of the court opinions and decisions and found that this term (October 2017) was high with 23%, but there were often years very low. Last year, 5-4 decisions made up 10% of all cases, and the year previous to that it was 5%. Within the past 15 years, the October 06 term was the most divisive, with 1/3rd of the cases being 5-4 splits. Ideological splits (that is, Liberal verses conservatives) are the highest cause for the split court, but that doesn't mean all cases go to the conservatives. For example, of the four cases that were 5-4 in the Oct15 term, 3 were considered the liberal court victories to the conservative's one.

SCOTUSBlog lists one of three classifications for the 5-4 split Conservative (the four Conservative Justices plus Kennedy) Liberal (the four liberal justices plus Kennedy) and Other (Any combination of Conservative, Liberal, and Kennedy).

In the past 8 terms (Oct10 - Oct17) Liberals scored the highest percentage of 5-4 decisions in 3 out of 8 years. Conservatives scored the highest percentage in 4 out of 8. Other has never recieved the highest percentage of decisions. In Oct11 all three categories received an equal share of 5-4 decisions (33% of all decisions each). Oct17 (this past term) is the only term where liberals achieved no 5-4 decision victories. It was the best year of the sample for conservatives, where they had 73% of the decisions but the best year for any group of justices was Oct15, where Liberals took 75% of all 5-4s.

TL;DR: Most of the 5-4s of any year are ideologically motivated, but this split was only 100% for one year since Oct05 Court.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .