textabstractIn the year 2000 some $142 billion in royalties were paid internationally by users of a specific piece of knowledge that were protected under Intellectual Property Right law (IPR) to those parties that owned these rights. Under current circumstances where knowledge & innovation play an increasingly significant role in the economy (Foray & Lundvall 1996, Cowan, David and Foray 2000, Cooke 2002, Dolfsma & Soete 2006, Dolfsma 2005). IPRs have become increasingly prominent in debates and are almost unanimously deemed to favor economic development by policymakers, and certainly by policymakers in developed countries. While it has been acknowledged that some parties may benefit more from a system of IPRs than others, in relative terms a Pareto improvement is the expected outcome (Langford 1997). This has not always been the case. In addition, the academic (economic) community is almost unanimous about the system of IPR overshooting its goals. This has been the motivation to include IPRs in the WTO negotiations. The TRIPS agreement (Trade-Related Aspects of Intellectual Property Rights) has resulted in 1994 from these negotiations. Especially during the 1990s the number of patents granted has grown tremendously despite the fact that many a scholar still supports Machlup’s (1958, p.28) conclusion that: “it would be irresponsible, on the basis of our present knowledge of its consequences, to recommend instituting one. But since we have had a patent system for a long time, it would be irresponsible, on the basis of our present knowledge, to recommend abolishing it.” From other corners, where specific effects of IPRs are considered, a different and less circumspect sound may be heard. Examples of this are attempts to make available HIV/AIDS drugs at a reduced price compared to what the pharmaceutical companies that have the patents on these drugs demand. I will focus on patents. Empirical and theoretical findings bearing on the question of IPRs’ effect on technological development, and thus prospect for economic development, are reviewed. Static and dynamic effects are distinguished. Areas where static effects may be expected include transfer of knowledge, balance of payment effects, effects for large as opposed to small firms, and effect on the ‘extent of the market’. Areas for dynamic effects include technological development and technological preemption. The list may not be exhaustive, and effects are interlocking: they may be mutually reinforcing or they may conflict. I will mostly focus on ‘dynamic’ effects.