PATENT LENGTH AND THE TIMING OF INNOVATIVE ACTIVITY
研究了专利长度与宽度对创新时机的影响，发现有限期限但更宽的专利能更好地激励社会最优的创新时机，从而减少无限期专利的必要性。
The standard result in patent policy, as demonstrated by Gilbert and Shapiro (1990), is that infinitely lived but very narrow patents are optimal as deadweight losses are minimised and spread through time but inventors can still recover their R&D expenditures. By extending their innovative environment to include timing as an important choice, we demonstrate that a finitely lived, but broader, patent can be socially desirable. This is because a patent breadth is a better instrument than length to encourage socially optimal timing. Thus, patents need not be infinitely long in order to encourage a greater number of inventions