1

Abstract — Dense networks among organizations are expected to work as a conduit of resources and knowledge within regional clusters. In this paper, we originally constructed a large database of interfirm networks in eighteen regions in Japan, and compared their inner structures. There is a marked difference among regions in their network structures. The variance is large especially among regions with small number of firms, and as the cluster size increases network structure improves. These results indicate that activities to support regional networking is necessary especially for small clusters. In those clusters, there is a room to improve networking We also analyze the characteristics of hub firms in each region and found that the headquarters location of the hub firms are strongly correlated with topological measures of networks. This suggested that high concentration of headquarters in Tokyo can hamper regional networking in the rest of the country. Index Terms—regional clusters, innovation, network