The era was marked by mysterious envelopes. When opened, the official-looking documents inside informed the reader that, because he owned three shares of, say, Microsoft Corp. stock some years ago, he was part of a class of plaintiffs. The class had already brought a lawsuit against Microsoft for a problem the reader had never noticed. Now the settlement was being divided, and the reader might be entitled to something. But the reader, disheartened by the sheaf of forms asking for details about a barely remembered transaction, usually tossed the notice in the trash and started flipping through that day’s Pottery Barn catalog.

Those envelopes are disappearing. Securities class actions are on the wane. For decades, corporate America fought them hard, writing checks to settle cases with one hand, and checks to K Street lobbyists with the other. But the plaintiffs proved tenacious, and the cases kept coming.