Sequential innovations with unobservable follow-on investments

?We consider a cumulative innovation process in which a follow-on innovator invests in R&D activities that influence both the expected commercial value as well as the novelty of its innovation. When the second innovator investments are not servable,licensing of the first innovation never occurs efficiently, and, at the equilibrium, the follow-on innovator either underinvests or overinvests. We show that a large patent breadth may be harmful for the first innovator too, and therefore Pareto-dominated;as long as the undervinvestment problem becomes more pronounced, the value generated by the follow-on innovator reduces, and so do the licensing revenues of the first inventor.