Justices split along ideological lines in a controversial ruling that some see as a blow to workers' rights.
More than 8% of U.S. public companies were hit with a shareholder class-action suit in 2017, a nine-year high.
The Supreme Court seeks to clarify whether workers can be compelled to sign agreements that prevent them from banding together to sue employers.
For plaintiffs' lawyers, it's growing easier to get wage-and-hour cases certified and to win settlements from employers.
A number of class-action cases that probably would have been decided in companies' favor are now up in the air.
