The Statistics of Supreme Court Splits

Not to diverge into politics — okay, a little — but there is a nice Cass Sunstein piece in today’s NY Times about people’s misperception of the likelihood of 5–4 Supreme Court vote splits. Sure, the current appointment is important, but as Cass points out, the percentage of Supreme Court decisions that have split 5–4 has sat at around 20% for decades. It’s not a new phenomenon. Matter of fact, it’s entirely predicable if you have basic understanding of statistics and small-group behavior.