中文摘要
本文考察在存在政策预期的情况下，专利期限对研发和创新的影响；政策预期在现实中普遍存在。本文采用双重差分设计，利用1995年《与贸易有关的知识产权协定》（TRIPs）获批所引致的美国不同技术领域专利期限的准实验变异。尽管平均专利期限普遍延长，但在大多数领域，创新者未来的创新成果仍面临相当大的专利期限缩短概率。本文得到三个主要发现：（1）在政策实施前，专利期限缩短概率较高、即平均专利期限延长幅度较小的领域，研发和创新的加速幅度更大。（2）这种更为活跃的研发和创新活动在政策实施后至少持续5年，其驱动力来自间接效应：与政策消息相关的加速通过与累积性知识创造相联系的技术外部性，促进了进一步的创新。（3）相反，若不存在政策预期的间接效应，专利期限延长幅度较小所产生的直接效应会激励相对较少的创新。
Abstract
Abstract I examine the impact of patent term on R&D and innovation in the presence of policy anticipation, common in real-world settings. Using a difference-in-difference design, I exploit quasi-experimental variation in US patent term across technological fields due to the ratification of TRIPs agreements in 1995. Despite a general increase in average patent term, in most fields innovators faced a considerable probability of patent term reduction for future innovations. Three key findings emerge: (1) R&D and innovation accelerate more in fields with a higher probability of patent term reduction, i.e. a shorter average patent term extension, before implementation. (2) This heightened activity persists for at least 5 years postimplementation, driven by indirect effects where the news-related acceleration fosters further innovation through technological externalities linked to cumulative knowledge creation. (3) Conversely, the direct effect of a shorter extension in patent term would stimulate relatively less innovation, absent the indirect effects of anticipation.