When do global pipelines enhance knowledge diffusion in clusters?

Recent studies have stressed the role played by global pipelines in fostering cluster growth and innovativeness. This paper develops a formal model investigating when global pipelines contribute to increase local knowledge, depending on various cluster characteristics such as size, knowledge endowment and ease of internal knowledge transmission. This model is an extension of Cowan and JonardÕs 2004 model in which we introduce the concept of cluster and a role for spatial proximity in knowledge diffusion. We find that there is a natural tendency of actors within global pipelines to act as external stars rather than knowledge gatekeepers. Global pipelines are beneficial for cluster knowledge accumulation only if the cluster is either characterized by a high quality local buzz or is small and weakly endowed in terms of knowledge.