This paper provides a direct measure of the density of patent thickets based on patent citations. We discuss the algorithm that generates the measure and present descriptive results validating it. Moreover, we identify technology areas particularly affected by patent thickets.

Post-grant validity challenges at patent offices rely on the private initiative of third parties to correct mistakes made by patent offices. We hypothesize that incentives to bring post-grant validity challenges are reduced when many firms benefit from revocation of a patent and when firms are...

This paper examines which firms from a heterogeneous pool are more likely to join together and form a research joint venture (RJV). It differs from previous contributions as it introduces a set of realistic hypotheses on the characteristics of research co-operation and information sharing....

We analyze the effect of patent thickets on entry into technology areas by firms in the UK. We present a model that describes incentives to enter technology areas characterized by varying technological opportunity, complexity of technology, and the potential for hold-up in patent thickets. We...

Complex high technology industries are increasingly affected by patent thickets in which firms' patents mutually block the use of important technologies. Firms facing patent thickets patent intensively to acquire bargaining chips and use licensing to ensure freedom to operate. Such licensing...

We investigate incidence and evolution of patent thickets. Our empirical analysis is based on a theoretical model of patenting in complex and discrete technologies. The model captures how competition for patent portfolios and complementarity of patents affect patenting incentives. We show that...

This paper is a study of licensing in a patent thicket. In a patent thicket licensing allows firms to avoid hold-up. It will have different effects on firms' R&D incentives depending on whether firms license existing or future patents. Building on a model of a patent portfolio race, firms'...

This paper introduces a model of coordination of research paths into the theory of Research Joint Ventures (RJVs). A comparison of RJVs and licensing by non-cooperative firms shows that the latter may be unable to co-ordinate on complementary research paths whereas RJVs are always able to do...

In a patent thicket licensing provides a mechanism to either avoid or resolve hold-up. Firms' R&D incentives will differ depending on how licensing is used. In this paper we study the choice between ex ante licensing to avoid hold-up and ex post licensing to resolve it. Building on a theoretical...