Productivity Spillovers among Knowledge Workers in Agglomerations: Evidence from GitHub

Software engineering is a field with strong geographic concentration, with Silicon Valley as the epitome of a tech cluster. Yet, most studies on the productivity effects of agglomerations measure innovation with patent data, thus capturing only a fraction of the industry's activity. With data from the open source platform GitHub, our study contributes an alternative proxy for productivity, complementing the literature by covering a broad range of software engineering. With user activity data covering the years 2015 to 2021, we relate cluster size to an individual's productivity. Our findings suggest that physical proximity to a large number of other knowledge workers in the same field leads to spillovers, increasing productivity considerably. In further analyses, we confirm the causal relationship with an IV approach and study heterogeneities by cluster size, initial productivity and project characteristics.