Preemption,leapfrogging and competition in patent races

This paper investigates when patent races will be characterized by vigorous competition and when they will degenerate into a monopoly. Undersome conditions, a firm with an arbitrarily small headstart can preempt its rivals. Such ‘?-preemption’ is shown to depend on whether a firm that is behind in the patent race, as measured by the expected time remaining until discovery, cant ‘leapfrog’ the competition and become the new leader. An example of an R&D game with random discovery illustrates how ?-preemption can occur when leapfrogging is impossible. A multi-stage R&D process allows leapfrogging and thus permits competition. A similar conclusion emerges in a model of a deterministic patent race with imperfect monitoring of rival firms' R&D investment activities.