When the Supreme Court granted certioriari in Dukes v. Wal-Mart Inc., the Vanderbilt Law Review grabbed a number of law professors who study mass torts and asked them to contribute essays to its En Banc feature. One of these–Richard Nagareda’s Common Answers for Class Certification–was one of the most interesting articles published in 2010. Several of the other contributions also posed some interesting questions, among them Alexandra Lahav’s The Curse of Bigness: The Optimal Size of Class Actions

Lahav doesn’t really address the question she asks in the title; she offers no verdict on the optimal size of a class action (unless the answer is "as big as you can make them"). For the most part, she focuses on how courts could use the promise of probabilistic evidence to justify certifying classes for litigation. But the introduction to her essay poses an interesting rhetorical issue: when arguing about class actions, does the size of the lawsuit matter?

There’s no question that many press outlets, when covering Dukes, focused on the fact that it was the largest civil-rights lawsuit to be certified.  After all, the size of the lawsuit is something the average reader understands immediately. And there is no question that courts often call attention to the size of class actions, both when granting certification and when denying it.

As Lahav correctly points out, there is no doctrinal limit on how large a class action may grow. (Rule 23(a)(1)–the numerosity requirement–does establish on how small one may shrink.) Instead, most lawyers use size as a proxy for one of the other Rule 23 requirements. Plaintiffs use the size of the class to bolster their arguments that a class action is superior to other forms of resolving a given dispute. For example, as the the Fifth Circuit put it in Jenkins v. Raymark Industries, when a class is large enough, it may be

superior to the alternative of repeating, hundreds of times over, the litigation of the state of the art issues with, as that experienced judge says, ‘days of the same witnesses, exhibits and issues from trial to trial.’

Defendants, on the other hand, often use size as a shorthand for heterogeneity (as they did in Dukes). As Lahav puts it:

The statements about the size of this class action appeal to an intuition that the court’s ability to provide individualized justice is inversely proportional to the size of the class action.

And, to the extent that a larger class is more likely to encompass various different kinds of claimants, that rhetoric can be useful. Defendants also may point out that the larger a class is, the more likely that it may pressure defendants into settling claims that have no merit, just to avoid the possibility of ruinous liability.

So does the size of a class matter? It depends on why the party is invoking it.