market-share theory.Antitrust. 1. A method of determining damages for lost profits by calculating the impact of the defendant’s violation on the plaintiff’s output or market share. Cf. BEFORE-AND-AFTER THEORY; YARDSTICK THEORY . [Cases: Monopolies 12(1.3). C.J.S. Monopolies §§ 28–37, 52, 64–66.] 2.Patents. A theory of lost-profits remedy offered when the patentee and the infringer share the market with a noninfringing competitor. • Using this method, the court assumes that the percentage of the market that the patentee holds is the same as the percentage of the infringer’s market that the patentee would have captured but for the infringement.

[Blacks Law 8th]