The Supreme Court’s decision in the Wal-Mart Stores, Inc. v. Dukes case (2011) was a major ruling concerning class-action lawsuits, particularly regarding the concept of commonality.

In the 2011 case Wal-Mart Stores, Inc. v. Dukes, the Supreme Court ruled against a group of female employees who attempted to file a class-action lawsuit against Wal-Mart for alleged gender discrimination in pay and promotions. The women claimed that Wal-Mart’s corporate culture allowed managers to exercise discretion in a way that systematically disadvantaged female employees. They research to represent a nationwide class of 1.5 million women, arguing that they were all affected by the same discriminatory practices. 

The key issue in the case was whether the plaintiffs met the legal requirement of commonality, which is essential in class-action lawsuits. Commonality means that all members of the class must share a common question of law or fact that can be resolved in a single stroke. The Supreme Court, in a 5–4 decision written by Justice Scalia, found that the women did not demonstrate a common issue tying all their claims together. Since decisions about pay and promotions were made by thousands of different managers across various locations, the Court ruled there was no single policy of discrimination that applied uniformly to all the plaintiffs. 

The Court emphasized that without a unifying “glue” holding the claims together, a class-action suit could not move forward. Because of the lack of commonality, the lawsuit was deemed too broad and diverse to be handled as a class. This decision significantly raised the bar for certifying class-action lawsuits, especially in employment discrimination cases, by requiring stronger evidence that the entire group suffered the same harm in the same way.