Analyzing the Spillover Mechanism on the Semiconductor Industry in the Silicon Valley and Route 128

To understand the impact of science and engineering innovations on economic growth requires relating discoveries to products, and identifying the scientists and engineers who are responsible for the knowledge transfer. Studies reliant on geographic proximity alone can show only that economic activity varies positively with the amount of research being done at a university [David (1992), Nelson and Romer (1996), Jaffe (1989,93)]. These "geographically localized knowledge spillovers" have proved unable to explain what it is about research universities that is crucial for their local economic impact (training, the research findings?) and, therefore, are unconvincing both to policy makers and the public. This paper analyses the spillover mechanism identifying its main components by analyzing the effect of university-based star scientists through explicit and implicit ties, and the effect of other neighbor firms, on the performance of semiconductor enterprises measured with patents. Explicit ties are modeled by the full and part-time job mobility of scientists located in universities; and implicit ties, by the presence of positive externalities or spillover effects to the firms of untied scientists at Universities in the same economic area. Specifically, this study examines the Silicon Valley and Route 128 cases in detail identifying the differences and similarities between these two major semiconductor regions in their spillover mechanisms. Previous research on high-technology industries has demonstrated the importance of geographically localized "knowledge spillovers" by building specific links between university scientists and firms and estimating the local effects of different types of links. This research goes an step forward, by not only measuring the effect of University research through the direct ties to firms (Zucker, Darby, Armstrong; 1998); but also measuring the importance of the inside industry R&D spillovers in the growth of the region.