Tuesday, October 7, 2008

It's like the SAT for Supreme Court justices...

Here's a nifty data thing.  Check out the Martin-Quinn scores for Supreme Court justice at http://mqscores.wustl.edu/.   This is a nifty application of a branch of statistics called item-response theory, which is most often used for designing standardized tests.  Just like the SAT designers peg students' "aptitude" from high to low based on their responses to questions, Martin and Quinn have pegged each justice on an ideological scale using their votes on various cases.

The Martin -Quinn site has a nice little graph showing all the justices and their ideological points over time.  (You can't miss it.  It animates over and over and over.)  Bonus points if you can name the Nixon appointee who trends way liberal in the 60's and 70's!

Data is downloadable, just in case you wanted 80 years of data about Supreme Court ideology.

1 comment:

Anonymous said...

Great post, and fascinating study. I'm a fan of IRT - more specifically the Rasch model; and of personal & economic freedoms related to education.

I was interested to note that the authors took a traditional liberal-conservative approach. Another approach that distinguishes between classical liberal personal freedoms; classical liberal economic freedoms; from more authoritarian approaches (e.g. "Worlds Smallest Political Quiz") might show different facets; and seems like a cleaner approach to operationalize the constructs.