We present a dynamic duopoly model of technical innovation in which R&D costs decrease exogenously with time and inter-firm knowledge spillover lowers the second comer's R&D cost. The spillover effect only becomes available after a disclosure lag. These features allow us to identify a new type of equilibrium: the leader delays investment until the R&D cost is low enough that the follower finds it optimal to invest as soon as he can benefit from the spillover. This equilibrium is subgame perfect over a wide range of parameters and raises several interesting implications. First, in our new equilibrium, the time delay between the two R&D investments is realistically short. Second, while the presence of a spillover favors the second-mover, this benefit is not enough to rule out a first-mover advantage. Indeed, the first-mover advantage survives whenever technical progress is sufficiently fast and the disclosure lag is relatively long. Third, in case of a major innovation, our equilibrium implies under-investment, which requires a substantial public intervention in favor of the investment activity.
A Dynamic Duopoly Model: When a Firm Shares the Market with Certain Profit
