Commonality (Rule 23(a)(2)) and predominance (one half of Rule 23(b)(3)) are often considered the heart of the class action certification inquiry. Rightly so, for they both strike at the real question a judge must ask: do the class members have enough in common to justify binding them all together in a single case? Through the 1990s and 2000s, predominance was considered the more important inquiry. In the 2010s, it appears that commonality is gaining ground.

Ten Cases to Bring You Up to Speed:

• Wal-Mart Stores, Inc. v. Dukes, 131 S.Ct. 2541 (2011).  
• Amchem Prods., Inc. v. Windsor, 521 U.S. 591 (1997).   
• Jamie S. v. Milwaukee Public Schools (7th Cir. 2012).
• Gates v. Rohm & Haas Co., 655 F.3d 255 (3d Cir. 2011).
• Sullivan v. DB Investments, Inc., 667 F.3d 273 (3d Cir. 2011).
• Pilgrim v. Universal Health Card, LLC, 660 F.3d 943 (6th Cir. 2011).
• Gintis v. Bouchard Transp. Co., Inc., 596 F.3d 64 (1st Cir. 2010).
• Avritt v. Reliastar Ins. Co., 615 1023 (8th Cir. 2010).
• In re Bridgestone/Firestone, Inc. Tires Prods. Liab. Litig., 288 F.3d 1012 (7th Cir. 2002). 
• Castano v. Am. Tobacco Co., 84 F.3d 734 (5th Cir. 1996).

Further Reading:

• * Richard Nagareda, Common Answers for Class Certification, 63 Vand. L. Rev. En Banc 149 (2010).
• * Ryan Patrick Phair, Resolving the "Choice-of-Law Problem" in Rule 23(b)(3) Nationwide Class Actions, 67 U. Chi. L. Rev. 835 (2000).
• * Alexandra Lahav, The Case For Trial By Formula (forthcoming, Texas L. Rev.)

Questions:

• * Why require a common answer? Why not just a common question?
• * Is there any way to certify a multi-state class action for trial?
• * What role does predominance play in a post-Dukes world?
• * How do you reconcile Gates v. Rohm & Haas Co. with Sullivan v. DB Investments, Inc.?