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:

Further Reading:


  • * 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.?