Correction of opinion count for Feb. 22 Sitting
Double checking my count, I found I missed one that was written by Justice Breyer. That makes the count 7 decided out of 13.
Writing two opinion apiece from that sitting: Kennedy, Sotomayer.
Writing one each: Stevens, Scalia, Breyer.
Not having released one yet: Thomas, Ginsburg, Alito, Roberts
[above updated in light of comment].