高科技行业越来越多地集中在少数昂贵的城市，“计算机科学”、“半导体”和“生物与化学”排名前十的城市，分别占发明者的70%、79%和59%。尽管成本较高，为什么发明家倾向于在同一领域的其他发明家附近选址?我使用了基于1971年至2007年美国专利领域的顶级发明家的纵向数据，以量化硅谷式集群的生产率优势及其对美国整体专利生产的影响。我将一个发明家在一年内产生的专利数量与本地集群的规模联系起来，本地集群定义为一个城市x个研究领域x年。我首先研究了纽约州罗彻斯特市(Rochester NY)的经验，由于其主要雇主柯达(Kodak)的倒闭，该市的高科技产业集群逐渐衰落。由于数码摄影的增长，柯达的就业在1996年后崩溃，导致罗切斯特高科技集群的规模下降了49.2%。我测试了集群规模的变化是否影响了柯达和摄影行业以外的发明家的生产力。我发现，在1996年至2007年期间，罗切斯特市非柯达公司的发明家的生产力相对于其他城市的发明家下降了20.6%，这是有条件的发明家固定效应。在本文的第二部分，我将转向基于样本中所有数据的估计。我发现，当一个发明家转移到一个更大的集群时，她产生的专利数量和收到的引用数量都会显著增加。 Conditional on inventor, firm, and city _ year effects, the elasticity of number of patents produced with respect to cluster size is 0.0662 (0.0138). The productivity increase follows the move and there is no evidence of pre-trends. IV estimates based on the geographical structure of firms with laboratories in multiple cities are statistically similar to OLS estimates. In the final part of the paper, I use the estimated elasticity of productivity with respect to cluster size to quantify the aggregate effects of geographical agglomeration on the overall production of patents in the US. I find macroeconomic benefits of clustering for the US as a whole. In a counterfactual scenario where the quality of U.S. inventors is held constant but their geographical location is changed so that all cities have the same number of inventors in each field, inventor productivity would increase in small clusters and decline in large clusters. On net, the overall number of patents produced in the US in a year would be 11.07% smaller.